U.S. President Donald Trump's envoy Steve Witkoff arrived in Moscow on Friday, Interfax news agency said, where he is expected to meet Russian President Vladimir Putin.
Witkoff has emerged as Washington's key interlocutor with Putin as Trump pushes for a deal to end the war in Ukraine, and has already held three long meetings with the Kremlin leader.
His latest visit to Moscow comes a day after Trump criticised a Russian missile and drone attack on Kyiv that killed at least 12 people, and posted on social media: "Vladimir, STOP!"
But Trump also said there had been significant progress in peace talks.
"This next few days is going to be very important. Meetings are taking place right now," Trump told reporters on Thursday. "I think we're going to make a deal … I think we're getting very close."
