Angela Rayner said the prime minister was “laser focussed on getting peace” and would continue “dialogue” with both President Donald Trump and Europe.

She said this was “a very serious moment” in the war and stressed the UK, along with its European allies, were focused on supporting Ukraine.

The US president made the decision to freeze US military support for Ukraine on Monday, after a meeting with members of his top team.

The US is by far the biggest individual donor of military aid to Ukraine, providing weapons, equipment and financial support.

Between the start of 2022 and the end of 2024, it gave $69bn (£54.6bn) in military aid, according to German think tank the Kiel Institute.

The decision came hours after Trump criticised Ukrainian President Volodymyr Zelensky for saying the end of the war with Russia is “very, very far away”.

The pair had an explosive spat in the Oval Office last Friday, with Zelensky leaving the White House before a proposed deal on sharing Ukrainian minerals with American companies could be signed.

On Monday, the White House announced it was “reviewing” the delivery of ammunition and other equipment to Ukraine to “ensure that it is contributing to a solution”.

Reacting to the decision, Rayner told the BBC the Trump administration wanted Europe to step up and had been clear about its intentions to end the war in Ukraine.

Rayner said the prime minister was also “laser-focused on getting peace”.

“He won’t be derailed by announcements,” Rayner told Radio 4’s Today programme.

“He will continue that dialogue with our oldest and strongest ally, the US, and with European partners and with Ukraine.”

Conservative leader Kemi Badenoch said the UK and Europe must “rearm faster” following the US announcement.

She said: “The news overnight that America is halting military aid to Ukraine is profoundly worrying.”

Over the weekend, Sir Keir hosted a summit of western leaders, as they scramble to shape peace negotiations and smooth over fractured relations between Trump and Zelensky.

The UK and France are taking a leading role and have both committed to send soldiers to Ukraine, under one proposal.

But apart from increasing spending on defence, there appears to be no consensus on a plan to end the war among European leaders.

A UK government spokesperson said: “We remain absolutely committed to securing a lasting peace in Ukraine and are engaging with key allies in support of this effort.

“It is the right thing to do, and is in our interest to do so.”