British Prime Minister Keir Starmer will meet Donald Trump on Thursday to plead for a U.S. backstop to any Ukraine ceasefire, insisting it would be the only way to stop Russia's Vladimir Putin from invading again.
Starmer arrived in Washington late Wednesday to build on a visit by French President Emmanuel Macron, amid growing concerns in Europe that the U.S. leader is about to sell Kyiv short in negotiations with Putin.
London and Paris are spearheading proposals to send a European peacekeeping force to Ukraine if Trump's shock decision to pursue talks with Russia's president brings a deal to end the war.
But they are calling for U.S. security guarantees in return, amid spiraling concerns in Europe that Trump is taking Russia's side and will sever the decades-old transatlantic alliance.
"The security guarantee has to be sufficient to deter Putin," Starmer told reporters on the plane to Washington.
"If there is a ceasefire without a backstop, it will simply give him the opportunity to wait and to come again, because his ambition in relation to Ukraine is pretty obvious."
The Europeans are seeking possible U.S. contributions like air cover, intelligence and logistics to support any troops sent to monitor a ceasefire.
The Oval Office meeting promises to be a clash of styles between the mild-mannered Labour leader, a former human rights lawyer, and the brash Republican tycoon.
Starmer, who will also hold a joint press conference with the U.S. president, has pitched himself as a "bridge" between Trump and Europe on Ukraine.
The British premier also comes bearing a gift for Trump.
His announcement Tuesday that UK defense spending will rise to 2.5 percent by 2027 was particularly aimed at the American leader, who has regularly presed European countries to pay more toward NATO.
- 'Nice guy' -
Starmer will meanwhile be hoping to avoid sweeping tariffs that Trump has promised to slap on the European Union.
But like Macron on Monday, he will have his work cut out to persuade Trump on Ukraine.
Last week Trump called Starmer a "very nice guy" -- but complained that he and Macron had done "nothing" to end the war in Ukraine.
The U.S. president stunned allies when he began negotiations with Russia, without including Ukraine or its European allies.
Concerns deepened when Trump attacked Ukrainian President Volodymyr Zelenskuy as a "dictator" and echoed Moscow talking points blaming Kyiv for Russia's February 2022 invasion.
Despite that, there have been growing signs of movement on a deal to end more than three years of bloody fighting.
Zelenskyy is due at the White House on Friday to sign a deal giving Washington access to Ukraine's rare minerals, which Trump has demanded as payback for U.S. military aid.
The Ukrainian president is hoping the deal will provide a guarantee of future U.S. support.
Starmer is then hosting Zelenskyy, Macron and other European leaders in Britain on Sunday as momentum grows.
With Britain and France proposing peacekeepers, the shape of a possible deal has begun to emerge -- but now it will be up to Moscow and Washington to seal it.
Trump has appeared cool on U.S. support for any backstop.
"I hope we have that problem where we can worry about peacekeeping. We've got to get there first," Trump told reporters on Wednesday.