US Secretary of State Marco Rubio has warned that Washington may “step back” from mediation efforts to resolve the war in Ukraine if Moscow and Kyiv do not present “concrete proposals.”

“Now we are at the time where concrete proposals need to be delivered by the two parties on how to end the conflict,” US State Department spokesperson Tammy Bruce told reporters at Tuesday’s Department press briefing—and quoting Rubio. “ If there is not progress, we [i.e. the US] will step back as mediators of the process.”

But the final decision on whether to continue diplomatic efforts will be made by US President Donald Trump, Bruce added.

Russian President Vladimir Putin had earlier proposed a three-day ceasefire between May 8 and 10 to mark Victory Day, but the Russian side had rejected calls from Washington and Kyiv for a 30-day ceasefire.

According to the State Department spokesperson, the US is not counting on a three-day ceasefire, but on a “complete, durable, ceasefire and an end to the conflict.”