The United States continues to warn that Russia could invade Ukraine “any day” amid escalating tensions in the region.

More than 150,000 Russian troops are estimated to be massed near Ukraine’s borders, U.S. President Joe Biden said Tuesday, as U.S. officials have urged all Americans to immediately leave Ukraine.

Biden said Tuesday that the U.S. has “not yet verified” claims by Russian President Vladimir Putin and the Kremlin that Russia was withdrawing some troops from near Ukraine’s borders.

ABC News has learned Putin had told his military forces to be ready to invade by Wednesday, but it remains unclear whether he has made a decision to attack his neighbor. Meanwhile, Ukrainian President Volodymyr Zelenskyy has called for a national day of unity Wednesday.

Russia has denied it plans to invade and has demanded the U.S. and NATO bar Ukraine from joining the military alliance.

Abc