"Tomorrow will be an important meeting, so I expect tomorrow, or soon after tomorrow, to have clarity on what collectively we can deliver," Rutte told journalists.

"That means that we can engage even more intensely, also with the American side to see what they want to deliver in terms of their participation."

Ukraine's President Volodymyr Zelensky will attend the talks in Paris on Thursday with leaders from a so-called coalition of the willing.

Spearheaded by France and Britain, the group of around 30 countries intends to provide support to Kyiv's military and possibly deploy some of its own soldiers to Ukraine if and when a ceasefire is agreed.

The deployment would aim to deter future Russian aggression.

US President Donald Trump, who has been pushing efforts to end the war, has said Washington could play a role supporting the Europeans.

But he has ruled out any American troops on the ground, and what exact commitments he would be willing to give remain vague.

Diplomats told AFP that European countries in the coalition were pushed to come up with concrete details on what they could contribute at a meeting of military chiefs last week.

French President Emmanuel Macron's office said Tuesday that there were now "enough contributions to be able to say to the Americans that we are ready to take our responsibilities as long as they take on theirs -- meaning giving European partners a 'backstop'."

That backstop could involve different aspects including intelligence, logistic support and communications.

Trump has been trying, so far in vain, to organise a summit between President Vladimir Putin and Zelensky, after having rolled out the red carpet for the Russian leader in Alaska last month.

On Tuesday, Trump said he was "very disappointed" with Putin for failing to move towards a peace deal on Ukraine.