President Trump’s war against Iran has depleted U.S. weapons stockpiles to troubling levels, siphoning supplies from Asia and Europe, according to senior officials.

The rapidly shrinking supply of air-defense missiles and other critical weaponry in Europe and Asia not only leaves the U.S. military less equipped, but could also leave Russia and China feeling emboldened should they contemplate a potential conflict with the United States, experts said.

Bombing Iran burned through thousands of multimillion-dollar missiles that contain precision parts from a global web of suppliers and can take years to produce. Defending against Iran’s retaliatory barrages has worn down U.S. stocks of air-defense missiles to an extent that has privately alarmed top officials in the Trump administration and has led to the United States’ delaying deliveries to European and Asian customers.

The Iran campaign has forced the Pentagon to rush ships, aircraft and air-defense units from across Europe and Asia to the Middle East, an effort with cascading consequences for equipment maintenance and troop morale, U.S. officials said. The result is a significant erosion of American firepower in those regions, a shift with long-term implications that are a growing concern in the military and intelligence communities, senior U.S. and Western officials said.

Karoline Leavitt, the White House press secretary, said the United States has “more than enough firepower to carry out any operation the president orders at any time and place.” But experts say the munitions crisis — part of which Mr. Trump inherited from President Joseph R. Biden Jr. — is almost certain to outlast his presidency.

Tom Karako, a senior fellow at the Center for Strategic and International Studies in Washington, said the depletion of munitions was a “generational annihilation of the means of conventional deterrence.” The impact on how decisions are made in Beijing and Moscow, he said, could resonate for years.

“It’s impossible for that not to have a significant effect on the decision calculus of Russia and China,” said Mr. Karako, who has been tracking U.S. weapons stockpiles. “They may do something quite deliberate and at the time of their choosing, because keep in mind — we’re going to take years to reconstitute.”

In meetings in the lead-up to the Iran war, Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, informed the president of the risks of dipping deeper into drained stockpiles, according to two officials with knowledge of the exchanges. Mr. Trump still decided to go ahead, believing the war would be over quickly. A spokesman for General Caine declined to comment on his private conversations with the president.

After attacking Iran alongside Israel on Feb. 28, Mr. Trump repeatedly promised victory within weeks. More than five months later, he remains unable to bend Iran to his will, or even to find a way to end the war. The munitions shortage is said to have played a role in persuading Mr. Trump to put aside a major bombing campaign late last month. But it also shows how the president’s decision to attack Iran has left the United States and its allies more vulnerable to other threats.

The Trump administration has worked with military contractors to try to accelerate and expand production. But even accounting for those efforts, it could take more than two years for the United States to replenish the more than 1,500 Patriot air-defense interceptor missiles that have been used in the Iran war. The current U.S. inventory of those missiles is fewer than 1,700, according to two people briefed on the stockpile who spoke on the condition of anonymity to discuss sensitive military details.

Mr. Trump has been enraged about news stories covering the munitions shortages. He has ordered a massive leak hunt across his government and is demanding criminal prosecutions. He has told advisers in private that any discussion of the munitions crisis signals weakness to the country’s enemies, and he continues in public to downplay the issue, deny it exists or blame his predecessor.

“Our defense companies are making more munitions than ever before, while rapidly expanding their plants and equipment at record levels,” Ms. Leavitt, the White House press secretary, said in a statement. “Anyone entrusted with access to classified military information who leaks it to the media is betraying that trust and breaking federal law, and should be prosecuted to the fullest extent of the law.”

Sean Parnell, the chief Pentagon spokesman, said reports of weapons shortages are false, adding that the United States has “everything required to strike at the time and place of the president’s choosing.”

The most immediate impact of the munitions shortage is being felt in Kyiv, the Ukrainian capital. President Volodymyr Zelensky of Ukraine said this week that the number of air-defense missiles being provided to his country by Western allies had dropped threefold this year compared with 2025. On Wednesday, Ukraine failed to intercept any of the 28 missiles fired by Russia, which killed at least 17 people. More interceptors, Mr. Zelensky said, “could have saved the lives of those killed today.”

The fundamental problem, analysts say, is that Russia has ramped up its missile production to a greater extent than Ukraine’s Western supporters have been able to manufacture air defenses. The Iran war exacerbated the mismatch.

Representative Jason Crow, a Colorado Democrat who sits on the House Armed Services and Intelligence Committees, said the “antiquated” U.S. defense procurement process “doesn’t allow us to actually keep pace with the rapidly evolving nature of warfare.”

“Frankly, our adversaries don’t have those hindrances,” Mr. Crow said.

The United States and its allies have begun to hoard air-defense missiles amid the global supply crunch. Mr. Trump, asked by a reporter in the Oval Office on Thursday about Mr. Zelensky’s plea for more missiles, shot back: “We want missiles too.”

Mr. Trump regularly insists that Mr. Biden’s support for Ukraine is to blame for any shortfalls in U.S. weapons stocks. He said on social media on Thursday that the United States had “massive amounts of ‘munitions,’ especially of certain types.”

It is true that the United States has a vast arsenal of less advanced munitions, including more than 100,000 guided bombs that are dropped from aircraft, according to the Center for Strategic and International Studies. The problem with many of those weapons is that they have to be released close to their targets, putting more warplanes at risk of getting shot down.

High-end cruise missiles avoid that risk because they can be launched from hundreds of miles away. But the U.S. military largely exhausted its stocks of certain types of long-range missiles — such as the Army Tactical Missile Systems, or ATACMS, and Precision Strike Missiles — during the Iran war, officials said.

Long-range missiles would be critical in a war against China or Russia, countries with far more advanced air defenses than Iran. Both governments are tracking U.S. stockpiles closely, estimating them through public sources like the congressional budget process and defense contractor announcements, as well as via their spy satellites and other surveillance systems, according to a U.S. official familiar with defense intelligence.

“The situation is shaping up very favorably,” a popular Russian pro-war blogger, Aleksandr Kots, recently wrote. “The less precision-guided weaponry the U.S. has, the less will reach Ukraine.”

Even if Mr. Trump’s successor wants to ramp up aid to Ukraine, Mr. Kots added, “doing so will be impossible with empty arsenals.”

The long-term impact of the depletion may be greatest in Asia, where the United States has long been preparing for the possibility of a Chinese invasion of Taiwan, the self-governing island that Beijing claims as its own. The U.S. military’s Indo-Pacific Command became a major source of munitions for the Iran war, with many of its Tomahawks and other long-range missiles in the region — critical to a fight with China — transferred from its stocks.

Hundreds of advanced air-defense interceptors have been sent to the Middle East from South Korea and elsewhere in Asia, while a carrier strike group and some of the Navy’s highest-end destroyers were deployed from the region to support the Iran campaign. U.S. troops in South Korea would be more vulnerable in a war with North Korea because the Pentagon has redirected tactical surveillance assets to the Middle East and withdrawn air defenses, a U.S. official said.

The depletion has wide-ranging effects. In Asia, some U.S. officials fear that South Korea and Japan will doubt the ability of the United States to protect them with nonnuclear defenses, and will be more inclined to seek their own nuclear weapons to establish more credible deterrence. In Europe, U.S. allies are already looking to increase weapons purchases from other countries, given the production backlog in the United States.

Russia and China have long understood that the U.S. stockpile is limited, officials say, and now understand that inventories will take time to be refilled to levels that would allow for the execution of certain war plans. In that sense, a more drawn-out Iran conflict benefits Moscow and Beijing, some analysts said.

“The longer this war runs and the more we continue to exchange fires with Iran, the worse the munitions problem becomes for the United States, and the larger and more visible this window of vulnerability becomes,” said Todd Harrison, a defense analyst at the American Enterprise Institute.

Dara Massicot, an expert on the Russian military at the Carnegie Endowment for International Peace, said that Moscow had already been reassessing its assumptions about U.S. military stockpiles before the start of the Iran war. The four years of conflict in Ukraine, she said, might have shown Russian military planners that the United States was slower at ramping up weapons production than they had believed.

“That’s the wrong kind of math to go into the Russian system, because then they start changing their perception of their own power vis-à-vis NATO,” said Ms. Massicot, who recently returned from a trip to Ukraine. “It causes them to come to conclusions that we may not want them to.”

Xinyun Wu contributed reporting from Taipei.