UK Prime Minister Keir Starmer has met with US President Donald Trump to discuss a long-term peace agreement for Ukraine, warning "it can't be peace that rewards the aggressor".
The British leader, who was described as a "tough negotiator" by Mr Trump after talks at the White House, said the UK was ready to deploy troops in support of a Ukraine peace deal.
"The UK is ready to put boots on the ground and planes in the sky [in Ukraine]," Mr Starmer said.
"Europe must step up. The UK is all in," he said, warning that any peace deal must "stop Putin coming back for more".
Mr Trump, who has alarmed Europeans with his sudden pivot towards Russia, said American leadership would be critical to maintaining peace in Ukraine should the three-year war end.
He also said he was confident that Russian President Vladimir Putin would not press to restart the war in the future.
“I think he’ll keep his word,” Mr Trump said of Mr Putin. “I’ve spoken to him, I’ve known him for a long time now."
Mr Trump played down an earlier rift with Ukrainian President Volodymyr Zelenskyy.
"I have a lot of respect for him," said Mr Trump, who had called the Ukrainian leader a dictator in a social media post last week.
"Did I say that? I can't believe I said that," he said.
Mr Zelenskyy is expected to visit the White House on Friday, US time, to sign a deal on US access to Ukrainian minerals.
Mr Trump also said he had had "very successful" back-to-back calls with Mr Putin.
Trump nonplussed by AUKUS reference
During the meeting Mr Trump was also asked about the AUKUS defence alliance between the US, UK and Australia.,
The president seemed unfamiliar with the term, replying to the journalist's question with: "What does that mean?"
When he was told it was a defence alliance with Australia, Mr Trump said his administration had "a great relationship" with Australia.
Mr Starmer said his talks with Mr Trump, which also included discussions on trade, were "productive".
The British leader also extended an invitation for Mr Trump to visit the UK on an "unprecedented" second state visit.
He said the invitation — a follow up to Mr Trump's earlier state visit when he was hosted by the late Queen Elizabeth during his first term in 2019 — was "truly historic".