It offered no suggestion that the hourlong call diminished the threat of an imminent war in Europe.

Biden also said the United States and its allies would respond "decisively and impose swift and severe costs" if the Kremlin attacked its neighbor, according to the White House.

The two presidents spoke a day after Biden's national security adviser, Jake Sullivan, warned that U.S. intelligence shows a Russian invasion could begin within days and before the Winter Olympics in Beijing end on Feb. 20.

Russia denies it intends to invade but has massed well over 100,000 troops near the Ukrainian border and has sent troops to exercises in neighboring Belarus, encircling Ukraine on three sides. U.S. officials say Russia's buildup of firepower has reached the point where it could invade on short notice.