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Friday, April 17, 2026

6 Common Medications That May Lower Your Dementia Risk

 

6 Common Medications That May Lower Your Dementia Risk

Several common medications, including vaccines, heart medications, and anti-inflammatory drugs, may lower the risk of dementia. While observational studies suggest a correlation, determining causation remains challenging. Vaccines, cholesterol and blood pressure medications, and diabetes drugs are being investigated for their potential protective benefits against dementia.

Some vaccines, along with heart medications and other drugs, appear to have a protective benefit.

An illustration of a figure looking at their reflection in an open medicine cabinet. On the upper shelf of the cabinet is a collection of medication bottles, pill blister packs, and a syringe.
Lorena Spurio

Getting your annual flu shot may come with a significant side benefit: helping to protect you from dementia.

Numerous studies have found that older adults who were vaccinated against the flu had a lower risk of developing dementia in the years that followed than those who had not been vaccinated. In one study, the risk was as much as 40 percent lower.

Research published earlier this month has bolstered that evidence, showing that older adults who were given a higher dose of the flu vaccine — commonly recommended for people 65 and over — had an even lower probability of developing Alzheimer’s disease compared with those who received the standard dose.

Other common medications have also been found to decrease people’s risk of dementia. The challenge for scientists, though, is determining whether the drugs are directly benefiting the brain or whether there’s just a correlation between them.

The flu vaccine is a good example of this. “People who tend to get vaccinated are the people who go to see a doctor, and then they follow the directions to take their blood pressure pills and cholesterol pills, which also reduce the risk of Alzheimer’s,” said Dr. Paul Schulz, a professor and neurologist at UTHealth Houston who led the new study.

But because everybody in that study got an influenza vaccine, and the higher dose offered more protection, the findings suggest there is something about the vaccine itself, rather than people’s behavior, that lowered the risk, Dr. Schulz said.

Here are a few more drugs that scientists are investigating for their potential to reduce dementia risk.

Shingles Vaccine

Excitement is especially high for the shingles vaccine, which has some of the strongest research behind it. Studies from around the world have found that people who received the vaccine had a lower risk of developing dementia, often by about 15 to 20 percent. Much of the research has been done on an older form of the vaccine, but at least one study indicated that a newer version more commonly prescribed in the United States, called Shingrix, could offer an even greater benefit. It (along with the flu vaccine) appears to be especially protective against dementia in women.

Researchers say they’re relatively confident that the vaccine itself is providing protection because its initial rollout in a few countries created a sort of natural clinical trial.

“I think at this stage, it’s a really compelling body of evidence of a cause and effect relationship,” said Dr. Pascal Geldsetzer, an epidemiologist at the Knight Initiative for Brain Resilience at Stanford who conducted some of the research.

There are a couple of theories about how vaccines might reduce the risk of dementia. One is that by protecting people from getting an infection, a vaccine prevents the immune response and especially the inflammation that comes with it. (Inflammation is a known contributor to dementia.) This may be especially relevant for shingles, since the virus initially replicates in the nervous system and can cause inflammation in the brain.

It’s also possible that the vaccines themselves might alter the immune system in a way that directly affects, and protects, the brain.

Cholesterol and Blood Pressure Medications

Several studies have found that both statins and drugs that treat hypertensionare associated with a roughly 10 to 15 percent reduced risk of dementia.

Many researchers think these drugs protect people’s brains by helping to manage blood pressure and cholesterol, both of which are risk factors for dementia. However, as with vaccines, people who consistently take their prescribed medications may have other healthy behaviors that could also lower their risk.

Most of the research is observational, but there have been a few clinical trials that have tried to more directly investigate the connection between these drugs and dementia. The results have been mixed. A 2025 trial from China found that people with high blood pressure who were given a medication for hypertension had lower rates of dementia four years later. But a 2009 trial that tested statinsin people who had vascular disease or were at high risk for it did not find a benefit in preventing cognitive decline.

There’s also an open question over whether people who don’t need the medications for heart health could take them for dementia prevention, said Geoffrey Joyce, a professor of pharmaceutical and health economics at the University of Southern California. There are two large trials currently investigating whether statins might be useful in this way.

Anti-Inflammatory Drugs

Since inflammation in the brain is a known contributor to Alzheimer’s, it’s conceivable that anti-inflammatory medications could provide protection by helping to reduce it in the brain as well as systemically. A recent large review paper listed anti-inflammatories as one of the classes of drugs that may reduce dementia risk.

David Llewellyn, a professor of clinical epidemiology and digital health at the University of Exeter Medical School in England who led the review, said he thought “the anti-inflammatory story” made sense scientifically.

But studies looking at the connection, especially with nonsteroidal anti-inflammatory drugs, have been mixed. Some have found a lower risk of dementia from ibuprofen use, while others showed no connection or even an increased risk. And a Cochrane review published in 2020 concluded there was “no evidence to support the use” of aspirin or other NSAIDs to prevent dementia.

Diabetes Drugs

Diabetes is associated with an increased risk of dementia, and a few drugs for Type 2 diabetes, including metformin and a class of medication called sodium-glucose cotransporter 2 (SGLT2) inhibitors, appear to modestly lower that risk, though some studies don’t show an effect.

The potential benefit is thought to largely stem from the medications’ ability to help control insulin and blood sugar levels, which affect brain cell health. There is also some evidence, mostly from animals, that the drugs help to reduce inflammation and may even lower levels of amyloid beta in the brain, a key protein involved in Alzheimer’s.

Clinical trials investigating whether these diabetes drugs can be beneficial in dementia are ongoing.

A few observational studies have also found that people with diabetes who took the newer GLP-1 medications had a lower risk of developing Alzheimer’s, even by as much as 45 percent, according to some reports.

Based on that evidence, and research in mice showing the drugs can reverse cognitive impairment, two clinical trials recently tested whether a pill form of Ozempic could also help slow cognitive decline in people with Alzheimer’s. But the trials found no benefit, and excitement about the use of GLP-1s as an Alzheimer’s treatment has died down significantly. More research is needed to determine if they indeed lower the risk of dementia.

Dana G. Smith is a Times reporter covering personal health, particularly aging and brain health.“

Thursday, April 16, 2026

Trump Administration Live Updates: Kennedy Testifies Before Congress

 

Trump Administration Live Updates: Kennedy Testifies Before Congress

What We’re Covering Today

  • “Health Department: Health Secretary Robert F. Kennedy Jr. is testifying before Congress on Thursday for the first time this year, starting a series of hearings on Capitol Hill that will set up the political debate over American health policy heading into the midterm elections. The first of two appearances on Thursday began with Mr. Kennedy assailing the policies of his predecessors and emphasizing his efforts to change Americans’ diets. His opening remarks steered clear of vaccine policy and other controversial actions the administration has taken. Read more ›

  • Homeland Security: The leaders of Customs and Border Protection, Immigration and Customs Enforcement and U.S. Citizenship and Immigration Services are appearing in front of the House Appropriations Committee. It is their first congressional hearing since Markwayne Mullin took over the Homeland Security Department, and questions around detention, enforcement and the future of mass deportation will be front and center.

Sheryl Gay Stolberg
April 16, 2026, 10:17 a.m. ET18 minutes ago

Secretary Kennedy told Representative Danny Davis, a Chicago Democrat and elder statesman of the Congressional Black Caucus, that the Trump administration is working to reduce maternal mortality among Black women — a point that Davis disputed, citing steep cuts to Medicaid, which covers 40 percent of all births. Kennedy also used his exchange with Davis to take a swipe at other members of Congress. “They’ve all shut me up,” Kennedy complained, adding, “They give a little speech that they can go and market, you know, for fundraising, and then they don’t allow me to answer the question.”

Sheryl Gay Stolberg
April 16, 2026, 10:03 a.m. ET33 minutes ago

President Trump’s grant of clemency to the nursing home entrepreneur Joseph Schwartz, who served only three months of a three-year sentence for tax crimes, has emerged as an issue in Secretary Kennedy’s appearance. Schwartz’s nursing home empire collapsed amid allegations of endangering residents and defrauding employees.

Representative Lloyd Doggett, Democrat of Texas, demanded to know why the president was treating wealthy people like Schwartz with leniency while the administration’s fraud efforts are directed at “the mother that’s trying to protect the sick child.” Kennedy sought to deflect the question.

Dani Blum
April 16, 2026, 9:56 a.m. ET39 minutes ago

Representative Mike Thompson, a California Democrat, asked the secretary if he has a medical degree — he said he does not — and accused Kennedy of undermining vaccines and “helping make diseases deadly again.” He showed a chart displaying rising measles cases in the country. As measles cases spread, public health experts now fear the U.S. will lose its measles elimination status.

Sheryl Gay Stolberg
April 16, 2026, 9:47 a.m. ET48 minutes ago

The committee chairman, Representative Jason Smith, a farmer and Missouri Republican, gave the secretary a not-too-subtle warning not to pursue policies that would reduce farmers’ yields. Kennedy is a strong proponent of regenerative farming, and the Trump administration has been roiled by debates over the weedkiller glyphosate, which is used by many American farmers but is a suspected carcinogen. “I would like to stress the importance of modern agriculture practices in producing a healthy, affordable and sustainable food supply,” Smith said.

Dani Blum
April 16, 2026, 9:36 a.m. ET59 minutes ago

The secretary said he was bringing on new members of the U.S.P.S.T.F., an influential task force that plays a key role in making preventive screenings and medications accessible to millions of Americans. The committee has not met since March 2025. 

Dani Blum
April 16, 2026, 9:31 a.m. ET1 hour ago

In his opening statement, Robert F. Kennedy Jr. turned to his familiar talking points, saying that Americans are facing an epidemic of chronic disease fueled by past policies. He emphasized new dietary guidelines and the push to phase out some food dyes, while staying away from vaccines and the more controversial actions the administration has taken.

The three most politically powerful men in America — President Trump, Vice President JD Vance and Speaker Mike Johnson — have intensified their criticism of Pope Leo XIV, who has repeatedly spoken about Roman Catholic Church teaching against war and for peace in recent days.

Their fight is not simply political. It is fundamentally religious, as the Republican leaders are now arguing with the pope over theology to support the U.S. and Israeli military campaign in Iran.

Hamed Aleaziz
April 16, 2026, 10:27 a.m. ET8 minutes ago

Senior Department of Homeland Security officials now testifying before the House Appropriations Committee have lamented the ongoing shutdown of the agency. “Seven months into the fiscal year, C.B.P. has been shut down more than we’ve been open,” said Rodney Scott, head of the U.S. Customs and Border Protection.

Tony Romm
April 16, 2026, 10:22 a.m. ET13 minutes ago

Senator Lindsey Graham, Republican of South Carolina and chairman of the chamber’s budget committee, sketched out his party’s latest thinking about the future of immigration and military spending. At a hearing on the president’s 2027 budget, Graham said that he hoped to invoke the special legislative process known as reconciliation to fund border patrol and I.C.E. “through the president’s term.” That limited package, he said, was meant as a response to an ongoing shutdown at the Department of Homeland Security.

Graham also recommended that Congress could handle extra money for defense — including the war in Iran — as part of a supplemental funding package that would be coupled with “some things that my Democratic colleagues want.” But if that falls, Graham said that he would encourage President Trump to pursue “another reconciliation bill for defense.”

The United States military said it had struck a boat in the eastern Pacific Ocean on Wednesday, killing three people that it accused of smuggling drugs.

The U.S. Southern Command, which oversees military operations in Latin America and the Caribbean, announced the strike on social media. It shared a 20-second video showing a boat engulfed with bright light as it moves through water. Seconds later, the boat appears to continue floating while aflame.

The California Supreme Court on Wednesday ordered the lawyer John Eastman disbarred for his role in seeking to overturn the 2020 election in favor of Donald J. Trump. 

Mr. Eastman had concocted a legal strategy to put forward fake electors for Mr. Trump in several swing states that the candidate had lost in order to have Congress block or delay certification of Joseph R. Biden Jr.’s victory on Jan. 6, 2021.“

The Slow-Motion Battle for Hormuz

 

The Slow-Motion Battle for Hormuz

“Iranian threats hobbled shipping through the Strait of Hormuz during the war, moving what little remained north into its own waters.

Before war Feb. 18–27

After Iranian retaliation April 3–12

Now the U.S. has mounted a blockade of its own, redrawing the board once again.

After the U.S. blockade

Strait of

Hormuz

U.S. ships enforcing blockade in Gulf of Oman

The American blockade aims to upend a dynamic that had become the new normal in the Strait of Hormuz since the United States and Israel launched the war in late February: Iran allowed ships carrying its own cargo to pass through the strait, even as it attacked commercial vessels and effectively halted shipping from almost everybody else.

Though Iran was getting much-needed revenue from the Iranian-linked oil tankers it allowed to pass, the U.S. allowed them to keep transiting the strait. The goal was to temper the sharp increases in oil prices tied to the war.

Most ships leaving the Persian Gulf came from Iranian ports

Where ships exiting the strait after the war began last loaded cargo, oil or gas

Ships coming from Iranian ports Other ports Unknown

Note: Only ships that were loaded when exiting through strait are shown. Ships leaving other ports may also have Iranian ties, but their last port was not recorded as Iran. Ships entering the Persian Gulf are not shown. Source: Kpler. The New York Times

On Monday, the United States imposed its own naval blockade, intent on ending Iran’s dominance of the waterway and cutting off its oil income by blocking all traffic to and from its ports.

More than 12 American military vessels were stationed in international waters in the Gulf of Oman, beyond the strait, a U.S. official said on Tuesday. And the military is likely monitoring the region from a distance, using radar, patrol aircraft and drones, said Jennifer Parker, a former naval officer now at the University of Western Australia’s Defense and Security Institute.

Since the U.S. blockade took effect, no ships linked to Iran have been spotted leaving the region, according to the vessel‑tracking company Kpler.

Some ships appeared to have slowed or stopped. And at least two that had links to Iran, and are the target of U.S. sanctions, appeared to have turned around back toward the Persian Gulf as of Wednesday. One of the ships that reversed course, the Rich Starry, a Chinese tanker, was spotted traveling eastward through the strait on Tuesday toward open water before making a U-turn.

Some ships without links to Iran did move through the strait on Monday and Tuesday, according to U.S. Central Command and companies like Kpler. The vessels stayed close to the Omani coast, keeping a distance from possible sea mines in the middle of the waterway.

A precise accounting of how many vessels are crossing the strait is difficult, because vessels can hide or falsify information about their location, according to maritime intelligence experts.

How Iran, then the U.S., changed shipping

Vessel traffic in the strait slowed almost immediately after the United States and Israel attacked Iran on Feb. 28, from around 130 ships per day to just a handful.

But even ships without ties to Iran may remain hesitant to attempt a passage. Amid fears that Iran may attack commercial vessels in response to the U.S. blockade, many shipping companies have been unwilling to risk the crossing. That might not change in the absence of a longer-term deal between the United States and Iran.

Around 900 ships have been bottled up in the Persian Gulf over the course of the war, according to a New York Times analysis of Kpler data.

How long ships have been stranded in the Persian Gulf

Since start of war 10 to 42 days Less than 10 days

OMANU.A.E.OMANQATARKUWAITIRAQIRANSAUDIARABIABAHRAINPersian GulfGulf of OmanStrait ofHormuz

Note: Shows ship positions on April 12. Time spent in the Persian Gulf based on data from mid-February through April 12. The analysis includes oil tankers, cargo ships and gas carriers with a recent position in the Persian Gulf, excluding ships making routine deliveries between ports within the gulf. Source: Kpler (shipping data) The New York Times

The standoff between the United States and Iran has spread concern that the vessels will be there even longer, giving the Iranians the upper hand, said Andreas Krieg, a senior lecturer in the School of Security Studies at King’s College London.

“We’re getting to a place where everyone is very desperate, so the Iranians are trying to milk it as long as they can,” Mr. Krieg said. “I think we'll have months and months of disruption around the Strait of Hormuz.”

Done and Dusted? Trump’s Portrayal of the War in Iran Collides With Reality.

 

Done and Dusted? Trump’s Portrayal of the War in Iran Collides With Reality.

“President Trump is attempting to portray the Iran war as a success, claiming a “regime change” and a new, reasonable regime. However, analysts believe the war has strengthened Iran’s hard-line military and emboldened the regime, which is not yielding to U.S. demands on its nuclear program. Despite Vice President Vance’s efforts to negotiate a “grand bargain,” Iran is leveraging its position, demanding concessions on issues like the Strait of Hormuz.

President Trump is confronting a crisis that is not bending to his narrative of a “pretty reasonable” new regime in Iran and all-but-assured victory for the United States.

President Trump gives a thumbs up as he stands on tarmac.
President Trump in Miami last week. Mr. Trump has declared a “regime change” accomplishment in Iran, even though analysts believe the war may have only increased the internal sway of Iran’s Islamic Revolutionary Guards Corps.Tierney L. Cross/The New York Times

President Trump is trying to cast his Iran war as all but over, a done-and-dusted success.

But after years of trying to impose his own reality on the world, he has now run into a crisis that is not bending to his narrative.

“It’s a new regime,” Mr. Trump said in a Fox Business interview that aired on Wednesday, referring to Iran’s new leaders. “We find them pretty reasonable to be honest with you, by comparison pretty reasonable.”

It was the latest instance of Mr. Trump’s trying to spin a “regime change” accomplishment in Iran, even though analysts believe the war may have only increased the internal sway of Iran’s Islamic Revolutionary Guards Corps, the hard-line military force that has long been a major player in Iran’s politics and economy. The new supreme leader, Ayatollah Mojtaba Khamenei, has not been seen in public since he replaced his father, who was killed at the start of the war, but his elevation as head of state has been another symbol of continuity.

“Most generously you could say there is a leadership change,” said Behnam Ben Taleblu, the senior director of the Iran program at the Foundation for Defense of Democracies, a Washington think tank with a hawkish stance on Iran. “It is incorrect for the proponents of the conflict to frame this as a change for the better.”

Indeed, trade through the Strait of Hormuz remains far from normal and Iran’s government is not bending to Mr. Trump’s demands on its nuclear program.

But in Mr. Trump’s telling, U.S. victory in Iran is already clear. In the Fox Business interview, reprising his frequent comments of the last two weeks, Mr. Trump asserted that Iran’s navy, air force and antiaircraft equipment had all been wiped out, along with many top officials. If Iran did not rule out nuclear weapons, Mr. Trump said, “we will be living with them for a little while, but I don’t know how much longer they can survive.”

In fact, analysts say, the 40 days of U.S.-Israeli bombardment that ended with last week’s cease-fire appear to have increased the power of the military and hard-liners in the Iranian system. Despite the widespread destruction and the killings of officials by the U.S. and Israeli militaries, the Iranian regime is acting emboldened, having demonstrated that it can wreak havoc in global trade and send U.S. gas prices soaring.

A woman crossing Enghelab Square in Tehran under a billboard of Mojtaba Khamenei, Iran’s new supreme leader.Arash Khamooshi for The New York Times

The result is that a president who has long relied on threats and bluster as essential foreign-policy tools seems to be groping for the leverage to bring Iran’s regime to heel. Analysts say that the success of the administration’s latest effort, its blockade of Iranian ports, depends on the ability of the United States and its allies to withstand the additional pressure that Iran could impose on Persian Gulf trade in response.

Mona Yacoubian, a former State Department official and Middle East expert, drew a contrast in Mr. Trump’s struggle with Iran to his success in exacting concessions from U.S. allies by threatening them with tariffs.

“This is not something he has control over with the stroke of a pen,” said Ms. Yacoubian, who directs the Middle East program at the Center for Strategic and International Studies, a Washington think tank. “This is where the president’s approach of his own charismatic and powerful personality, in my view, is not a match for the complexity, the opacity, that is the case with Iran.”

The administration has been eager to portray a groundbreaking deal with Iran as being possible. Vice President JD Vance said Tuesday that Mr. Trump sought a “grand bargain” in which the United States would treat Iran “economically like a normal country” if it acted “like a normal country.”

After 21 hours of talks last weekend, Vice President JD Vance left Pakistan without reaching an agreement with Iranian officials.Pool photo by Jacquelyn Martin

“He doesn’t want a small deal,” Mr. Vance said.

Mr. Vance ended an extensive session of talks with Iranian officials in Pakistan last week without an agreement. He said Tuesday that the United States would keep negotiating, and that “the people we were sitting across from wanted to make a deal.”

But Iran appears to have taken note of the leverage it has against Mr. Trump, given the pain of rising gas prices and Republican worries that the unpopularity of the Iran war could hurt the party in the midterm elections in November. That means that even though Iran appears ready to negotiate, its leaders could make demands of their own on matters like the future governance of the Strait of Hormuz, while still driving a hard bargain on nuclear policy, the issue that matters most to Mr. Trump.

Nate Swanson, a former U.S. official who was on the Trump negotiating team with Iran until July, said the regime in Tehran was not going to capitulate to Mr. Trump’s demands in negotiations, “just as they did not on the battlefield.” Mr. Trump was unlikely to succeed, he said, in “trying to force transformational change on a system that feels like it just won a war.”

“Iran will only make a deal they see as being in their interest,” Mr. Swanson, now at the Atlantic Council, said. “That will most likely be small and transactional.”

Mr. Swanson also cautioned against reading too much into the perceived pragmatism of individual Iranian negotiators like Mohammad Bagher Ghalibaf, the parliament speaker whom Mr. Trump has cast as part of a more moderate, new crop of Iranian leaders. Without a consolidated power base, all Iranian officials will need to emphasize their hard-line bona fides, he said.

“It’s not in Ghalibaf’s or anyone else’s interest to stray from the party line right now,” Mr. Swanson said.

Anton Troianovski writes about American foreign policy and national security for The Times from Washington. He was previously a foreign correspondent based in Moscow and Berlin.”

Lawrence: Trump says 'nobody has ever ended one war.' Is that the stupidity or insanity speaking? - YouTube

 

Wednesday, April 15, 2026

I Predicted This War in 2024 — Now I'm Predicting How It Ends | Prof. Jiang Xueqin

 

Trump’s Blockade Risks Upending an Emerging Détente With China - The New York Times

Trump’s Blockade Risks Upending an Emerging Détente With China

"In a thinly veiled critique of the war in Iran, China’s leader said the world could not risk reverting “to the law of the jungle.”

President Trump meeting with China’s leader, Xi Jinping, in South Korea last October. They will meet again next month.Haiyun Jiang/The New York Times

By David E. Sanger and Tyler Pager

David E. Sanger has covered five American presidents and was a Times foreign correspondent in Asia for six years. Tyler Pager is a White House correspondent.

When China declared on Monday that the U.S. blockade of Iranian oil leaving the Strait of Hormuz was “dangerous and irresponsible,” it was a brief window into President Trump’s latest challenge: how to keep the Iran conflict from upending an emerging détente with China.

Mr. Trump is expected to land in Beijing in four weeks, in what was imagined as a carefully planned, highly orchestrated effort to recast the relationship between the world’s two largest economies.

The president has already delayed the trip once, and White House officials insist there is no discussion of putting it off again, even if the United States is still choking off Iranian oil exports. Ninety percent of those exports — more than 1.3 million barrels per day — were purchased by China before the American and Israeli attack began on Feb. 28.

At first the Chinese were relatively quiet about the military action, knowing that the shipments already at sea and an impressive stockpile of emergency reserves of oil would likely tide them through. They ignored Mr. Trump’s demand that China send warships to keep the strait open. They produced standard-issue calls for both sides to stand down.

But once the blockade began on Monday, and facing the prospect that Chinese-flagged cargo ships, some manned by Chinese crews, could be turned away by the U.S. Navy, the tone shifted.

China’s leader, Xi Jinping, made his first public comments on the war on Tuesday, saying that the world could not risk reverting “to the law of the jungle.” He never mentioned the United States or Mr. Trump. But he did not need to, adding during a meeting with the crown prince of Abu Dhabi that “to maintain the authority of international rule of law, we cannot use it when it suits us and abandon it when it doesn’t.”

Want to stay updated on what’s happening in China and Iran? , and we’ll send our latest coverage to your inbox.

It was a clear reference to Mr. Trump, who in January told The New York Times that “I don’t need international law,” adding, “I’m not looking to hurt people.” He made it clear that he would be the arbiter of when international legal constraints applied to his actions.

China’s foreign ministry, playing its accustomed role in signaling between Washington and Beijing, took a tougher line, accusing the United States of a “targeted blockade” that “will only aggravate confrontation, escalate tension, under the already fragile cease-fire, and further jeopardize safe passage through the Strait of Hormuz.”

For his part, Mr. Trump is ignoring the criticism and pretending — at least in public — that the Chinese government is somehow applauding his action.

“China is very happy that I am permanently opening the Strait of Hormuz,” he wrote on Wednesday morning on his social media account. “I am doing it for them, also - And the World,” he continued, predicting that Mr. Xi would “give me a big, fat, hug when I get there in a few weeks.”

But Mr. Trump also said that he had protested to Mr. Xi after U.S. intelligence agencies had obtained information that China might have sent a shipment of shoulder-fired missiles to the Iranians, for use in the conflict. The intelligence was not definitive, and there is no evidence that Chinese missiles have been used against U.S. or Israeli forces.

Nonetheless, Mr. Trump told Fox News in an interview broadcast Wednesday that he had written to Mr. Xi to seek assurances that Chinese arms were not being sent to Iran to be used against American and Israeli forces. And he wrote in his social media post that “they have agreed not to send weapons to Iran.”

The communications were kept private, so it is not possible to verify the Chinese commitment, or to determine if it came with any caveats. But Mr. Trump’s tone was more positive than it was about a week ago, when the revelation of the weapons shipment intelligence led Mr. Trump to threaten that “if we catch them doing that, they get a 50 percent tariff,” employing his go-to threat against any country defying his will.

The exchange underscored how delicate the relationship is right now — and how the Iran conflict threatens to upend it.

“President Trump has created the circumstance where two of his biggest goals are in direct conflict,” said Kurt Campbell, a former deputy secretary of state under President Joseph R. Biden Jr. and the chairman of the Asia Group, which he founded.

“One is to monitor and control all cargo coming through the strait, which includes China’s,” he said. “And the other is his desire for a manifestly positive visit to Beijing.”

Mr. Trump’s ambassador to China, David Perdue, was in the Oval Office late on Tuesday, discussing the upcoming visit. National security officials said that before the Iran conflict broke out, Treasury Secretary Scott Bessent had negotiated the outlines of economic initiatives the two countries would announce.

Far less progress has been made on the major security issues, according to U.S. officials, including how to talk about the future of Taiwan, or China’s fast-growing nuclear arsenal, or its military buildup in the South China Sea and the confrontations it has sparked with the Philippines.

With a month to go before Mr. Trump lands in Beijing, it is still unclear how the two leaders will structure a conversation about the blockade — if it is still in force — or about the display of U.S. military power that began with the seizure of Nicolás Maduro of Venezuela, then proceeded with Mr. Trump’s attack on Iran.

But there is considerable evidence the Chinese military is intently focused on how the United States pulled off both attacks. Chinese officials appear concerned about the speed at which the Iranian leadership was decapitated in the opening hours of the war.

“There is a lot of speculation about what can break the U.S.-China détente, and undermine the summit,” said Rush Doshi, an assistant professor at Georgetown University and former adviser to Mr. Biden on China. “It hasn’t been issues like A.I. chips, or even rare earths,” he added, referring to two areas of intense competition between the two nations. “But it could be Iran.”

The blockade, Mr. Doshi said, could “create awkward dynamics” if there is a confrontation between the Navy and commercial Chinese ships, though both have seemed eager to avoid that. “And the second is reports that China is considering sending lethal assistance to help Iran,” which senior congressional and intelligence officials appear to take seriously.

David E. Sanger covers the Trump administration and a range of national security issues. He has been a Times journalist for more than four decades and has written four books on foreign policy and national security challenges.

Tyler Pager is a White House correspondent for The Times, covering President Trump and his administration."

Trump’s Blockade Risks Upending an Emerging Détente With China - The New York Times