President Trump on Monday temporarily suspended the delivery of all U.S. military aid to Ukraine, senior administration and military officials said, just days after Mr. Trump and President Volodymyr Zelensky of Ukraine had an explosive confrontation at the White House.
The order affects more than $1 billion in arms and ammunition in the pipeline and on order. It resulted from a series of meetings at the White House on Monday between Mr. Trump and his senior national security aides, the officials said, speaking on the condition of anonymity to discuss internal deliberations.
The officials said the directive would be in effect until Mr. Trump determined that Ukraine had demonstrated a good-faith commitment to peace negotiations with Russia.
Mr. Trump’s decision dramatically escalates the breach between Washington and Kyiv, at a critical moment in the conflict. The most immediate beneficiary of the move is President Vladimir V. Putin of Russia. If the suspension is lengthy, he can use the time to press for further territorial gains. And he may well decide to hold back from any negotiations at all, figuring that any prolonged dispute between Mr. Trump and Mr. Zelensky will only strengthen his position, either on the battlefield or when cease-fire talks ever take place.
Mr. Trump’s move has few direct precedents in recent American history. While the United States has paused the transfer of specific weapons systems to allies and partners, such as President Joseph R. Biden Jr.’s decision to suspend deliveries of 2,000-pound bombs to Israel that he feared could be used against civilians in Gaza, a full cutoff is essentially an ultimatum. It forces Mr. Zelensky to agree to a cease-fire on terms Mr. Trump dictates, or condemns the country to larger battlefield losses.
The suspension also puts the United States in direct opposition to its major NATO allies. Most of the largest European nations, led by France, Britain and Germany, have pledged to step up aid to Ukraine in recent days, siding with Mr. Zelensky in his dispute with the Trump administration. But they simply do not have the stockpiles to make up the difference in the short term.
Mr. Trump’s directive, which was reported earlier by Bloomberg News, also halts deliveries of equipment from Pentagon stockpiles as aid through the Ukraine Security Assistance Initiative, which provides funds that Kyiv can use only to buy new military hardware directly from U.S. defense companies. It was unclear what exactly Mr. Zelensky would need to do for Mr. Trump to resume the military assistance.
Mr. Trump has increasingly aligned himself with Mr. Putin and his narrative about the war in Ukraine. He falsely claimed that it was Ukraine that started the war and has called Mr. Zelensky, who was democratically elected, a “dictator.”
He has called Mr. Putin “smart” and “cunning,” but declined to call him a dictator. And Mr. Trump has spoken in recent days about how he and Mr. Putin have been bonded by going through the shared ordeal of the investigation into Moscow’s attempts to tilt the election eight years ago to Mr. Trump. American intelligence officials concluded at that time that Mr. Putin’s intelligence agencies worked actively to swing the 2016 election in Mr. Trump’s favor, a conclusion that Mr. Trump has rejected and called part of the “Russia hoax.”
The tensions between Mr. Trump and Mr. Zelensky exploded into the open on Friday, when the two men were supposed to sign a deal at the White House for Ukraine to turn over rare mineral rights to repay U.S. military aid over the past three years. Instead, Mr. Trump and Vice President JD Vance berated Mr. Zelensky in front of the cameras for not being grateful enough for U.S. support.
The fate of the minerals deal remained unclear.
Mr. Trump said on Monday that he did not think the minerals deal was dead, calling it a “great deal for us,” but that there was one thing he needed to see from Mr. Zelensky to restart negotiations.
“I just think he should be more appreciative,” Mr. Trump told reporters.
Earlier in the day, Mr. Trump seized on comments Mr. Zelensky made over the weekend when he predicted that a peace deal with Russia was “still very, very far away.”
“This is the worst statement that could have been made by Zelenskyy, and America will not put up with it for much longer!” Mr. Trump wrote on social media.
On Monday, several members of Mr. Trump’s cabinet continued to join with allies in suggesting that Mr. Zelensky was responsible for the diplomatic breakdown, and should show remorse for the Oval Office episode.
Commerce Secretary Howard Lutnick said in an interview on CNN on Monday that it was “way too far” for Mr. Zelensky to demand, as part of any deal, “reparations” and the return of seized land from Russia and security guarantees.
“You’ve got to say, ‘We love America, we appreciate America, we want you by our side, and if you think we should have peace, we should have peace,’” Mr. Lutnick said.
“That’s not a peacemaker,” Mr. Lutnick said of Mr. Zelensky, “that’s a troublemaker.”
Mr. Lutnick suggested that Mr. Trump was still committed to brokering a deal between Ukraine and Russia, and “beat both sides down to get them to the table.”
In the aftermath of the Oval Office meeting, the Trump administration immediately began having discussions about cutting off or reducing military assistance, training and possibly military intelligence support for Ukraine, a senior official said on Friday. It was unclear late Monday whether Mr. Trump also directed officials to curtail intelligence sharing, although one senior official said it was still flowing — for now.
Mr. Trump convened a meeting of members of his national security team on Monday to discuss the administration’s options.
The decision comes at a critical moment in Ukraine’s war against Russian aggression, and as Mr. Trump has made clear in recent weeks that the days of isolating Moscow are over.
Through its own weapons production and arms deliveries from Europe, Ukraine could withstand a U.S. shutdown from some weeks, even a few months, U.S. officials and analysts said on Monday.
“The reality is that Ukraine is far less dependent on the United States for its day-to-day combat needs than it was a year ago,” said Michael Kofman, a senior fellow at the Carnegie Endowment for International Peace, who has visited Ukraine several times since the war started three years ago.
But if the halt in deliveries went longer, Ukraine would lose its supply of some advanced weapons, including advanced air-defense systems, surface-to-surface ballistic missiles and long-range rocket artillery. The United States also provides Ukraine with parts, maintenance and technical support.
Mr. Zelensky has said that cutting off military assistance would be a devastating blow but would not end the fighting.
“The contribution from the United States to Ukraine’s defensive capability and security is now around 30 percent,” he said during an interview last month. “You can imagine what would happen to us without this crucial 30 percent.”
U.S. military aid stopped flowing to Ukraine last year for several months after Mr. Trump pressed his Republican allies in Congress to withhold assistance.
The effects were first felt in the nightly aerial bombardments that Russia directed at energy infrastructure across the country. With the launching tubes of American air defense systems empty, air defense teams could do little to defend against Russia’s most sophisticated missiles as they laid waste to the nation’s thermal power plants.
As aid was delayed month after month, metro stations in the capital were crowded with families seeking shelter as the blanket of protection provided by American Patriot batteries began to fray.
The impact on the front took more time to be felt. But as supplies dwindled and American-made Howitzers fell silent, Ukrainian commanders fighting in the area said they were forced to ration ammunition.
Adam Entous contributed reporting from Washington, and Marc Santora from Kyiv, Ukraine.
