Secretary of State Marco Rubio warned Tuesday that the United States will end mediation unless Russia and Ukraine make "concrete proposals" on ending the war, his spokeswoman said.
"We are now at a time where concrete proposals need to be delivered by the two parties on how to end this conflict," State Department spokeswoman Tammy Bruce told reporters, in what she said was a message from Rubio.
"If there is not progress, we will step back as mediators in this process."
She said it would ultimately be up to President Donald Trump to decide whether to move ahead on diplomacy.
Russian President Vladimir Putin recently proposed a three-day ceasefire around Moscow's commemorations of the end of World War II — but has rebuffed a Ukrainian-backed U.S. call for a 30-day ceasefire.
The United States wants "not a three-day moment so you can celebrate something else — a complete, durable ceasefire and an end to the conflict," Bruce said.
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