Biden vows to act ‘decisively’ if Russia invades Ukraine

President Joe Biden conferred on Sunday with Ukraine’s leader over the Russian troop buildup near its border, promising that the U.S. and allies will act “decisively” if Russia further invades the Eastern European nation.

Biden and President Volodymyr Zelenskyy’s call came as the U.S. and Western allies prepared for a series of diplomatic meetings to try to de-escalate a crisis that Moscow said could rupture ties with Washington.

“President Biden made clear that the United States and its allies and partners will respond decisively if Russia further invades Ukraine,” White House press secretary Jen Psaki said in a statement following the call.

Psaki added that Biden underscored his commitment to the principle of “nothing about you without you,” the tenet that it won’t negotiate policy that impacts Europe without its allies’ input.

Biden has spoken of hitting Russia with economy-jarring sanctions if it moves on Ukraine’s territory, but he said last month that U.S. military action is not on the table.

The Kremlin has demanded that any further expansion of NATO exclude Ukraine and other former Soviet countries. The Russians have also demanded that the military alliance remove offensive weaponry from countries in the region.

The White House has dismissed Russia’s demands on NATO as a non-starter. A key principle of the NATO alliance is that membership is open to any qualifying country. And no outsider has membership veto power. While there’s little prospect that Ukraine would be invited into the alliance anytime soon, the U.S. and its allies won’t rule it out.

Zelenskyy said in a Twitter posting after Sunday’s call that “keeping peace in Europe, preventing further escalation, reforms, deoligarchization were discussed.”

“We appreciate the unwavering support,” Zelenskyy said.

The United States has made little progress in efforts to persuade Russian President Vladimir Putin to ease tensions. Senior U.S. and Russian officials are scheduled to meet Jan. 9-10 in Geneva to discuss the situation.

Biden spoke with Putin for nearly an hour on Thursday. He told reporters the next day that he warned Putin that his economy would pay a “heavy price” if Russia made further moves against Ukraine.

CAROLYN KASTER/ASSOCIATED PRESS President Joe Biden arrives to board Air Force One at Delaware Air National Guard Base in New Castle, Del., on Monday en route to Washington, D.C.