US President Donald Trump's return to the White House has raised the spectre of some kind of halt in the fighting after he vowed to end the war -- though he has never explained how.

Speaking at the World Economic Forum in Davos a day earlier, Zelensky said any deal to end the conflict would need to be overseen by a large foreign contingent of peacekeepers.

Zelensky said that given the small size of the Ukrainian army compared to that of Russia, "we need contingents with a very strong number of soldiers" to secure any peace deal.

"From all the Europeans? Two hundred thousand. It's a minimum. Otherwise, it's nothing," he said.

He said any other arrangement would be akin to the monitoring mission led by the Organization for Security and Co-operation in Europe (OSCE) in eastern Ukraine that disintegrated when Russia launched its full-scale invasion in February 2022.

"They had offices and that's all," Zelensky said, underscoring the need from the Ukrainian perspective for an armed force to prevent further Russian attacks.

The Ukrainian leader has repeatedly said that Ukraine must be represented at any talks with international parties to end the conflict and that only robust security guarantees can dissuade Russia from attacking again.

Ukraine's fear that Moscow would use a truce to rebuild its military stems partially from the decade that followed peace agreements between Kremlin-backed separatists and Kyiv in 2014 which failed to halt Moscow's full-scale invasion in 2022.

In an earlier address at Davos, Zelensky called on Europe to establish a joint defence policy and said European capitals should be prepared to increase spending, while calling into question Trump's commitment to NATO, the US-led security bloc.

Trump on Tuesday indicated he would consider imposing fresh sanctions on Russia if President Vladimir Putin refuses to negotiate a deal to end the war in Ukraine.