Donald Trump has warned Volodymyr Zelenskiy he is “gambling with World War Three” in a heated exchange at the White House, amid UK efforts to broker an American security guarantee for Ukraine.

The US president met his Ukrainian counterpart in the Oval Office as the two nations were set to sign a deal granting the US access to rare minerals in exchange for further military aid.

But the agreement was not signed after a series of testy remarks between the two presidents.

Keir Starmer is preparing to discuss how to guarantee that a peace deal in Ukraine will last when he meets Mr Zelenskiy and other European leaders in Downing Street this weekend.

The relationship between the Ukrainian leader and Mr Trump remains tense, after the US president last week accused Mr Zelenskiy of being a dictator.

As the US president met his counterpart in the Oval Office, their discussions became heated.

“You’re gambling with millions of people … You’re gambling with World War Three,” Mr Trump said.

Mr Zelenskiy warned the US would “feel it in the future” if it did not continue to support Ukraine.

“Don’t tell us what we’re going to feel. We’re trying to solve a problem,” Mr Trump hit back.

US vice president JD Vance questioned why Mr Zelenskiy had not said thank you for US military aid during the meeting.

Mr Vance was also heard to say to the Ukrainian leader: “Mr President, with respect, I think it’s disrespectful for you to come into the Oval Office and try to litigate this in front of the American media.

“Right now, you guys are going around and forcing conscripts to the front lines because you have manpower problems. You should be thanking the president for bringing an end to this conflict.”

Mr Zelenskiy left the White House early, putting on hold plans for he and Mr Trump to sign the minerals deal.

A news conference featuring the two leaders was also called off.

Writing on his Truth Social platform, Mr Trump said his Ukrainian counterpart was “not ready for peace if America is involved, because he feels our involvement gives him a big advantage in negotiations”.

In a sign that the relationship between the two leaders could be salvaged, Mr Trump added: “I don’t want advantage, I want peace. He disrespected the United States of America in its cherished Oval Office. He can come back when he is ready for peace.”

Mr Zelenskiy meanwhile thanked the president on X following the meeting.

“Thank you America, thank you for your support, thank you for this visit. Thank you (Mr Trump), Congress, and the American people. Ukraine needs just and lasting peace, and we are working exactly for that,” he said.

Downing Street had welcomed the proposed US-Ukraine minerals deal, and said it would “bind” Washington to Kyiv.

The fractious meeting comes after Mr Starmer and French president Emmanuel Macron travelled to Washington DC for talks with Mr Trump.

The British and French leaders sought to charm the US president and were met with a warm welcome.

Ahead of Sunday’s summit in London focused on security, the British Prime Minister will meet with Mr Zelenskiy separately.

A Downing Street spokesman said on Friday that “the UK has made it clear that we’ll play our full part in ensuring a just and lasting peace deal on Ukraine’s terms, backed up by strong security guarantees”.

The continued diplomacy push over the weekend comes after Sir Keir’s meeting with Mr Trump at the White House on Thursday.

The US president has resisted calls to fully commit American military might to guarantee any Ukraine peace deal, but suggested closer economic ties and an agreement on mineral access between Kyiv and Washington would effectively act as a security “backstop”.

Mr Starmer returned to the UK on Friday following a trip to the White House which went as well as No 10 could have hoped, with Mr Trump clearly pleased with the King’s invitation for an unprecedented second state visit, giving an indication that he would not block the Chagos Islands deal and suggesting a trade deal could spare British exports from US tariffs.

World leaders rallied to express solidarity with Mr Zelenskiy following the White House clash.

Polish Prime Minister Donald Tusk said on X that Ukraine and its leader were “not alone”.

Mr Macron said “we all were right to have helped Ukraine and sanctioned Russia three years ago, and to continue to do so”.

“There’s an aggressor, which is Russia, and a people attacked, which is Ukraine,” the French president added as he spoke to reporters.

They were followed by similar messages from a host of other European leaders, including EU Commission president Ursula von der Leyen, and German chancellor Olaf Scholz.

Conservative leader Kemi Badenoch called for “respectable diplomacy” following the meeting, and said a “divided West only benefits Russia”.