US Secretary of State Marco Rubio said on Friday that Washington could soon exit efforts to reach a Ukraine ceasefire if it decided peace was not "doable", after meeting European and Ukrainian officials in Paris.

European powers have been seeking a seat at the table since US President Donald Trump's shock decision to open talks with Russia to end its three-year-old war.

But Trump's push for peace has stumbled, with Russian President Vladimir Putin rebuffing a complete truce.

"The United States has been helping Ukraine over the last three years, and we want it (the conflict) to end, but it's not our war," Rubio said.

"We need to figure out here now, within a matter of days, whether this is doable in the short term, because if it's not, then I think we're just going to move on," he told reporters at the Le Bourget airport outside Paris.

"We have other priorities to focus on as well."

Rubio said European officials had been "very helpful and constructive with their ideas" during talks in Paris on Thursday, which he attended with US envoy Steve Witkoff.

"We'd like them to remain engaged... I think the UK and France and Germany can help us move the ball on this," he said, ahead of a similar meeting planned for "early next week" in London. (AFP)