Donald Trump has said he would like China's help to deal with Russia as he seeks to bring an end to the war in Ukraine.

"I'd like China to help us out with Russia," the US president said on board Air Force One, as he flew to Asia for a whirlwind tour, where he will meet China's Xi Jinping in South Korea.

It could be wishful thinking, however. China is Russia's biggest ally, and a vital support to Moscow since Western sanctions were imposed over its war in Ukraine.

Trump's comments come off the back of a difficult week for Kyiv - the US refused to give it Tomahawk cruise missiles, EU leaders did not release frozen Russian cash to help fund its defence, and there have been more deadly strikes.

Ending the Russia-Ukraine war has become a focal point for Trump in recent months, with a ceasefire deal so far eluding him, despite his campaign promises to solve the situation quickly. A summit with Putin in August failed to yield any tangible results, and Trump has grown increasingly frustrated with Moscow.