President Joe Biden warned his Russian counterpart Vladimir Putin that the United States would respond decisively to any Ukraine invasion, the White House reported. The two leaders spoke for nearly an hour late Thursday amid growing alarm over Russia’s troop buildup near Ukraine. 

White House officials said that the call began at 3:35 PM EST and concluded 50 minutes later, after midnight in Moscow. 

“Biden urged Russia to de-escalate tensions with Ukraine. He made clear that the United States and its allies and partners will respond decisively if Russia further invades Ukraine,” the White House said. 

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Putin had requested the call, the second between the leaders this month, ahead of scheduled talks between senior U.S. and Russian officials set for January 10 in Geneva.

“President Biden also expressed support for diplomacy, starting early next year with the bilateral Strategic Stability Dialogue, at NATO through the NATO-Russia Council, and at the Organization for Security and Cooperation in Europe,” the White House statement further read. 

“President Biden reiterated that substantive progress in these dialogues can occur only in an environment of de-escalation rather than escalation.”

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Putin’s foreign affairs adviser, after the call, said Biden reaffirmed the US threat of new sanctions against Russia in case of an escalation or invasion, to which Putin responded with a warning of his own that such a US move could lead to a complete rupture of ties.

“It would be a colossal mistake that would entail grave consequences,” said Yuri Ushakov. He added that Putin told Biden that Russia would act as the U.S. would if offensive weapons were deployed near American borders.

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Russia has made clear it wants a written commitment that Ukraine will never be allowed to join NATO and that the alliance’s military equipment will not be positioned in former Soviet states, demands that the Biden administration has made clear are non-starters.

With inputs from the Associated Press