INTERNATIONAL: U.S. President Joe Biden and Russia's Vladimir Putin have spoken by phone for an hour on Saturday, February 12, after Washington and its allies have warned that Russian forces could invade Ukraine at any moment.

The White House has confirmed that President Joe Biden has spoken with President Vladimir Putin on Saturday, to make clear that if Russia further invades Ukraine, the U.S. and its allies will impose swift and severe costs on Russia. President Biden has urged President Putin to engage in de-escalation and diplomacy instead.

The U.S. State Department has ordered most of its embassy staff to leave Ukraine, adding to its call on Friday for private citizens to get out of the country within 48 hours. The Pentagon has said it was withdrawing about 150 military trainers.

In the latest effort to avert hostilities, the Biden-Putin call began at 11:04 a.m. Eastern time and ended at 12:06 p.m., a White House official has said.

Russia's military buildup near Ukraine and a surge of military activity has fueled fears that Russia could invade. Russia denies having any such plans.