US President Donald Trump has criticised European leaders as "weak" and suggested the US could scale back support for Ukraine.

In a wide-ranging interview with Politico, he said "decaying" European countries had failed to control migration or take decisive action to end Ukraine's war with Russia, accusing them of letting Kyiv fight "until they drop."

He argued that Russia held the "upper hand" and urged Ukrainian President Volodymyr Zelensky to "play ball" by ceding territory to Moscow.

In the UK, Downing Street rejected Trump's claim that Europe had failed to act, citing the UK's leadership on sanctions and reiterating support for the US-led peace process.

Trump claimed ideological divisions now threatened to fracture Washington's alliances.

Asked whether leaders he viewed as weak could still be allies, he replied, "It depends," adding, "I think they're weak, but I also think that they want to be so politically correct. I think they don't know what to do."

His latest public criticism of Europe comes as he looks to increase pressure on Zelensky and Kyiv's allies to end the war in Ukraine.

The president's remarks also came after his administration released its new 33-page National Security Strategy, which warned of Europe's potential "civilisational erasure" and questioned whether some nations could remain reliable allies.

Russia welcomed that strategy, which did not cast Russia as a threat to the US, as "largely consistent" with Moscow's vision.

The document also followed similar rhetoric to Trump's speech to the UN earlier this year, where he had harsh criticism for Western Europe and its approach to migration and clean energy.