Washington DC - President Donald Trump suspended US military aid to Ukraine on Monday, a White House official said, sharply escalating pressure on Kyiv to agree to peace negotiations with Russia.

The move comes just days after a stunning public clash between Ukrainian President Volodymyr Zelensky and Trump, who is seeking a rapid end to the war.

Trump earlier on Monday had declined to rule out a pause when quizzed by reporters, but any disruption in the flow of US arms to the front line would rapidly weaken Ukraine's chance of beating back Russia's invasion.

"The President has been clear that he is focused on peace. We need our partners to be committed to that goal as well," a White House official told AFP, speaking on condition of anonymity.

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"We are pausing and reviewing our aid to ensure that it is contributing to a solution," the official added.

Congressional Democrats immediately condemned the pause as dangerous and illegal.

"My Republican colleagues who have called Putin a war criminal and promised their continued support to Ukraine must join me in demanding President Trumpimmediately lift this disastrous and unlawful freeze," said Gregory Meeks, top Democrat on the House Foreign Affairs Committee.

Trump also warned he would "not put up" much longer with Zelensky's defiance, and said Ukraine's leader should be "more appreciative" of US support.

Speaking at the White House, Trump said Zelensky "won't be around very long" without a ceasefire deal with Moscow.

The pause has gone into effect immediately and impacts hundreds of millions of dollars of weaponry in the process of being sent to Ukraine, The New York Times reported.

Donald Trump Trump suggests Zelensky "won't be around very long" without ceasefire deal

Zelensky for his part said Monday he was seeking for the war to end "as soon as possible."

The comment came after Zelensky accused Russia – which invaded Ukraine in 2014 and greatly expanded the conflict in 2022 – of not being serious about peace.

The Ukrainian leader insisted tough security guarantees were the only way to end the war.

But Trump's stance has upended US support for Ukraine, and Washington's allies more broadly, and stoked concern about Washington pivoting to Russia.

After weekend crisis talks in London, Britain and France are investigating how to propose a one-month Ukraine-Russia truce "in the air, at sea and on energy infrastructure" – potentially backstopped by troops on the ground.

Zelensky said discussions were still focusing on the "first steps," adding: "An agreement on ending the war is very, very far away" – a comment that angered Trump.

Zelensky added in a video statement that "real, honest peace" would only come with security guarantees for Ukraine, which agreed to denuclearize in 1994 only in exchange for protection provided by the US and Britain.

"It was the lack of security guarantees for Ukraine 11 years ago that allowed Russia to start with the occupation of Crimea and the war in Donbas, then the lack of security guarantees allowed Russia to launch a full-scale invasion," Zelensky said.

Russia dismissed the comments, accusing Zelensky of not wanting peace – echoing US criticism after he was shouted down Friday in the Oval Office.

On the ground, Ukrainian officials reported fatalities from a Russian missile strike on a military training facility some 80 miles from the front line.

A respected military blogger said between 30 and 40 soldiers were killed and 90 more wounded in the attack near Dnipro on Saturday.

Trump has previously called Zelensky, president since 2019, a "dictator" for not holding elections, even though martial law precludes any vote because of the war.

Zelensky dismissed calls for him to resign, repeating his pledge to do so only if Ukraine were given NATO membership, which Russia – and now the US under Trump – opposes.

In Moscow, Kremlin spokesperson Dmitry Peskov blamed Zelensky for Friday's blow-up with Trump and Vice President JD Vance, saying he "demonstrated a complete lack of diplomatic abilities."

"He doesn't want peace," Peskov told reporters.

On Monday, Vance told broadcaster Fox News he was confident Zelensky would "eventually" agree to peace talks with Moscow.

"I think Zelensky wasn't yet there, and I think, frankly, now still isn't there," Vance said. "But I think he'll get there eventually. He has to."

Germany's likely next chancellor, Friedrich Merz, said the astonishing White House clash was a "deliberate escalation" by Trump.

US and Russian officials have held talks on ending the war, enraging Kyiv and Europe for being sidelined, and prompting fears that any deal could threaten Ukraine's future.