U.S. President Donald Trump will walk away from trying to broker a Russia-Ukraine peace deal within days unless there are clear signs that a deal can be done, U.S. Secretary of State Marco Rubio said on Friday.

"We're not going to continue with this endeavor for weeks and months on end. So we need to determine very quickly now, and I'm talking about a matter of days whether or not this is doable in the next few weeks. If it is we're in. If it's not, then we have other priorities to focus on as well," Rubio said in Paris, after meeting European and Ukrainian leaders.

Rubio said Trump was still interested in a deal but was willing to move on if there were no immediate signs of progress.