There is a “viable chance” of a ceasefire between Russia and Ukraine, Prime Minister Sir Keir Starmer has said, ahead of Friday’s summit between US President Donald Trump and Russian President Vladimir Putin.

The two presidents are meeting in Alaska to discuss ending the war in Ukraine.

Ukrainian President Volodymyr Zelensky and other European leaders, who are not attending the meeting, held a joint call with Trump to reiterate their position.

Sir Keir said Ukraine’s “territorial integrity” had to be protected and international borders “must not be changed by force”.

In another development, visiting US Vice-President JD Vance said it was Trump’s mission to “bring peace to Europe once again”.

Last week Trump warned there could be “some swapping of territories, to the betterment of both”, leading to fears Ukraine might have to give up some areas in order to end the bloody conflict.

Ukraine has insisted it will not accept Russian control of land it has seized, including Crimea, while Moscow wants to maintain control.

It also wants assurances that Ukraine will not join the Nato military alliance and a limit on the size of its army.

Addressing a virtual meeting of the European leaders following the call with Trump, Sir Keir said “any ceasefire would have to be lasting and to be lasting it would need security guarantees”.

“That is why we set up this coalition of the willing,” he added.

The coalition is a group of mainly European countries who have pledged to provide military support to Ukraine – including potentially boots on the ground – in order to deter Russia from breaching any agreed peace deal.

Sir Keir said the coalition had “credible” military plans ready that could be used in the event of a ceasefire.

He said the leaders of the group were also ready to increase economic pressure on Russia if necessary, for example through increasing sanctions.

He also praised Trump’s efforts to reach an agreement, saying: “For three-and-a-bit years this conflict has been going on and we haven’t got anywhere near the prospect of an actually a viable solution, a viable way of bringing it to a ceasefire.

“Now we do have that chance, because of the work the president has put in.”

Vance is currently on a private family holiday in the UK, and also joined the call with Sir Keir and other European leaders on Wednesday.

Later that evening, he gave an address at RAF Fairford in Gloucestershire to American troops stationed in the UK.

The vice-president said the two countries had a “beautiful alliance” and that the US had “worked with our friends from the United Kingdom to achieve great victories” over the past 100 years.

“It’s not just about going to war, and it’s not just winning when we do,” Vance added.

“When we fight together, when we make it clear that we always approach every situation with an open hand – but if things go poorly, we’re willing to do what we have to do, we make it easier to achieve peace and prosperity all over the world.”

Following the call with European leaders, Trump told a press conference there was a chance of a meeting between Putin and Zelensky.

He said he would use his initial meeting with Putin to “find out where we are and what we’re doing”, adding: “We’ll have a quick second meeting between President Putin and President Zelensky and myself, if they’d like to have me there.”

He also warned Putin that he would face “very severe consequences” if he did not agree to end the war after Friday’s summit.

Zelensky, who joined the call while in Berlin to meet German Chancellor Friedrich Merz, said the US was ready to continue its support of Ukraine and accused Russia of not wanting peace.

“Putin cannot fool us,” he said.