His comments came ahead of an expected gathering of European leaders in Paris on Monday, although France has yet to confirm the meeting.

Starmer will attend the get-together if it goes ahead, a UK official familiar with the matter told AFP on condition of anonymity.

In a statement, Britain's leader said: "This is a once in a generation moment for our national security where we engage with the reality of the world today and the threat we face from Russia.

"It's clear Europe must take on a greater role in NATO as we work with the United States to secure Ukraine's future and face down the threat we face from Russia."

Starmer, who is also expected to visit US President Donald Trump in Washington soon, added that the UK "will work to ensure we keep the US and Europe together".

"We cannot allow any divisions in the alliance to distract from the external enemies we face," he said.

Starmer's comments came after US Secretary of Defense Pete Hegseth warned on Friday that Europe needed to boost its defence spending because it cannot assume that the presence of American troops on the continent will "last forever".

They also come as European leaders scramble to force their way to the table at any talks to end Russia's war in Ukraine.

Trump upended the status quo this week when he announced he was likely to meet Russian leader Vladimir Putin soon to start talks to end the conflict, leaving US allies in Europe reeling from concerns that their interests would be sidelined in any deal on Ukraine.

The issue has dominated the ongoing Munich Security Conference, where senior European officials, Ukrainian President Volodymyr Zelensky, NATO chief Mark Rutte and US Vice-President JD Vance are among the attendees.

Rutte said the planned meeting in Paris "would focus on defence spending and planning so that "when a deal is reached in Ukraine, that we have absolute clarity what Europe can contribute".

A spokesman for French President Emmanuel Macron's office told AFP "discussions" were ongoing over a "possible informal meeting".