The White House says President Joe Biden warned Ukraine’s president Thursday that there is a “distinct possibility” Russia could take military action against Ukraine in February. The Kremlin likewise sounded a grim note, saying it saw “little ground for optimism” in resolving the crisis after the U.S. this week again rejected Russia’s main demands.

Russian officials said dialogue was still possible to end the crisis, but Biden again offered a stark warning amid growing concerns that Russian President Vladimir Putin will give the go-ahead for a further invasion of Ukrainian territory in the not-so-distant future.