Sir Keir Starmer has reaffirmed the UK will continue to back Ukraine’s “irreversible path” to joining Nato despite leading figures in President Trump’s administration appearing to rule out membership.

The prime minister told Ukraine’s President Volodymyr Zelensky he stood by a pledge made alongside ex-president Joe Biden at last year’s Nato summit in Washington, to support Ukraine’s bid for membership.

The two leaders spoke on the phone ahead of global leaders meeting at the Munich Security Conference.

Sir Keir’s comments are in stark contrast to those of the Trump administration, which has said this week that Nato membership for Ukraine is not a “realistic prospect”.

In a readout of the call, a Downing Street spokeswoman said: “The Prime Minister began by reiterating the UK’s concrete support for Ukraine, for as long as it’s needed.

“He was unequivocal that there could be no talks about Ukraine, without Ukraine.

“Ukraine needed strong security guarantees, further lethal aid and a sovereign future, and it could count on the UK to step up, he added.

“The prime minister reiterated the UK’s commitment to Ukraine being on an irreversible path to Nato as agreed by allies at the Washington Summit last year.”

The leaders agreed it was an “important moment to demonstrate international unity and support for Ukraine” and “agreed to stay in close contact”, the statement added.

The UK has had to walk a fine line between its support for Kyiv and maintaining good relations with President Trump, who this week agreed to open negotiations with Russian President Vladimir Putin while signalled his willingness to make concessions to Moscow.

Trump’s defence secretary, Pete Hegseth, has said restoring Ukraine’s territory to where it was before the first Russian invasion in 2014 is simply “not realistic”.

Speaking at a defence summit in Brussels on Wednesday, Hegseth also downplayed the prospect of Ukraine joining Nato.

His remarks were the clearest indication yet of the Trump administration’s position on the Ukraine war and what a peace plan to end the conflict could involve.

Ukraine has repeatedly called for Nato membership and has rejected ceding territory as part of any peace deal.

Nato’s official position is that Ukraine is on an “irreversible” path to joining the alliance, which was established at a meeting in Washington last year and signed off by Sir Keir and ex-president Biden.

Sir Keir also took a phone call from President Trump late on Thursday night, when they discussed “his forthcoming visit to the US”, No 10 said.

Zelensky has warned Putin is “definitely not preparing for negotiations”, but to “continue deceiving the world” as he appealed for unified pressure from allies on Russia.

Foreign Secretary David Lammy said he and US Vice President JD Vance would have talks on the sidelines of the Munich conference.

Stood next to Vance at a news conference, Lammy said the pair had “important issues to discuss on Ukraine and how we support Ukraine” during a “tough moment”.

Lammy said the UK was “committed to increasing defence and encourage our friends across Europe to do the same”.

Vance said their discussion would focus on what he and Lammy “spoke about a couple of years ago when we met, which is our shared belief that Europe really should take a bigger role in its own security”.