US president Joe Biden has warned his Russian counterpart Vladimir Putin that America could impose new sanctions against Russia if it takes further military action against Ukraine.
Mr Putin said such a move could lead to a complete rupture of ties between the nations.
The two leaders spoke frankly for nearly an hour on Thursday amid growing alarm over Russia’s troop build-up near Ukraine, a crisis that has deepened as the Kremlin stiffened its insistence on border security guarantees and test-fired hypersonic missiles to underline its demands.
Further US sanctions “would be a colossal mistake that would entail grave consequences,” said Mr Putin’s foreign affairs adviser Yuri Ushakov, who briefed reporters in Moscow after the Biden-Putin phone conversation.
He added that Mr Putin told Mr Biden that Russia would act as the US would if offensive weapons were deployed near American borders.
White House officials offered a far more muted post-call analysis, suggesting the leaders agreed there are areas where the two sides can make meaningful progress but also differences that might be impossible to resolve.
White House press secretary Jen Psaki said Mr Biden “urged Russia to de-escalate tensions with Ukraine” and “made clear that the United States and its allies and partners will respond decisively if Russia further invades Ukraine”.
Mr Putin requested the call, the second between the leaders this month, ahead of scheduled talks between senior US and Russian officials on January 9 and 10 in Geneva.
The Geneva talks will be followed by a meeting of the Russia-Nato Council on January 12 and negotiations at the Organisation for Security and Co-operation in Europe in Vienna on January 13.
White House officials said Thursday’s call lasted 50 minutes, ending after midnight in Moscow.
Mr Biden told Mr Putin the two powers now face “two paths”: diplomacy or American deterrence through sanctions, according to a senior administration official.
Mr Biden said the route taken, according to the official, will “depend on Russia’s actions in the period ahead”.
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 rejected.
Mr Biden told Mr Putin a diplomatic path remains open even as the Russians have moved an estimated 100,000 troops toward Ukraine and Kremlin officials have turned up the volume on their demands for new guarantees from the US and Nato.
White House officials said Mr Biden made clear that the US stands ready to exact substantial economic pain through sanctions should Putin decide to take military action in Ukraine.
Mr Putin reacted strongly, noting “that it would be a mistake that our ancestors would see as a grave error. A lot of mistakes have been made over the past 30 years, and we would better avoid more such mistakes in this situation,” Mr Ushakov said.
Russia’s demands are to be discussed during the talks in Geneva, but it remains unclear what, if anything, Mr Biden would be willing to offer Mr Putin in exchange for defusing the crisis.
Draft security documents Moscow submitted demand that Nato deny membership to Ukraine and other former Soviet countries and roll back military deployments in Central and Eastern Europe.
The US and its allies have refused to offer Russia the kind of guarantees on Ukraine that Putin wants, citing Nato’s principle that membership is open to any qualifying country.
They agreed, however, to hold talks with Russia to discuss its concerns.
The security proposal by Moscow has raised the question of whether Mr Putin is making unrealistic demands in the expectation of a Western rejection that would give him a pretext to invade.
Steven Pifer, who served as US ambassador to Ukraine in the Clinton administration, said the Biden administration could engage on some elements of Russia’s draft document if Moscow is serious about talks.
Meanwhile, key Nato members have made clear there is no appetite for expanding the alliance in the near future.
The US and allies could also be receptive to language in the Russians’ draft document calling for establishing new consultative mechanisms, such as the Nato-Russia Council and a hotline between Nato and Russia.
Mr Biden and Mr Putin, who met in Geneva in June to discuss an array of tensions in the US-Russia relationship, are not expected to take part in the January talks.
Last week, Russia test-fired Zircon hypersonic missiles, a move Russian officials said was meant to help make Russia’s push for security guarantees “more convincing”.
The test was the first time Zircon missiles were launched in a salvo, indicating the completion of tests before the new missile enters service with the Russian navy next year and arms its cruisers, frigates and submarines.
US intelligence earlier this month determined that Russian planning was under way for a possible military offensive that could begin as soon as early 2022, but that Mr Putin had yet to determine whether to move forward with it.