Britain and France will work with Ukraine on a plan to end the fighting with Russia, which will later be presented to the United States, Prime Minister Keir Starmer said on Sunday.

"The United Kingdom, along with France and possibly one or two others, will work with Ukraine on a plan to stop the fighting, and then we'll discuss that plan with the United States," Starmer told British media.

Starmer hosted Volodymyr Zelensky and European leaders on Sunday for a summit on the conflict, which has taken on huge significance in the wake of the clash between the Ukrainian president and US counterpart Donald Trump.

Starmer said "nobody wants to see" the scenes of the two leaders' White House clash, and that "I am clear in my mind that he (Trump) does want a lasting peace."

The prime minister has presented himself as a bridge between the United States and Europe, and met with Trump in Washington on Thursday.

"We have to find a way that we can all work together. Because, in the end, we've had three years of bloody conflict. Now we need to get to that lasting peace," Starmer said.

"There's a risk that (Russian President Vladimir) Putin will come again if he's given the opportunity to do so..., which is why I've been so centrally focused on what a guarantee is. How do we defend the line if a line is agreed," he added.

Where that physical line would be is "a subject for discussion", said Starmer. (AFP)