President Joe Biden has said that sending US troops to Ukraine in response to a Russian military buildup is "not on the table".
But he warned Russian president Vladimir Putin that there could be “severe consequences” if Russia launched an attack on Ukraine. In such a scenario, US would also provide “defensive” capabilities to Ukraine, he told reporters on Wednesday.
His comments came a day after he held talks by a video link with Mr Putin.
"It would depend upon what the rest of the NATO countries were willing to do as well," Mr Biden told reporters in his first response after talking with Mr Putin.
"But the idea the United States is going to unilaterally use force to confront Russia invading Ukraine is not ... in the cards right now."
Mr Biden said there were no “minced words” and he was “very straight-forward” in stating to Mr Putin that invasion of Ukraine could have economic consequences like “none he’s ever seen or have ever been seen”.
The virtual summit was held between the two leaders to ease tensions between Moscow and Washington and to avert a potential military crisis in Ukraine, a former Soviet republic that has tilted toward the West since 2014.
Washington has been raising concerns over Russia’s major military buildup near Ukraine's eastern border while Russia has accused Ukraine of provocation and denied intentions of invasion.
Mr Putin highlighted the threat from NATO "that was undertaking dangerous attempts to gain a foothold on Ukrainian territory, and building up its military capabilities along the Russian border". He emphasised the importance of legally binding guarantees to prevent NATO’s eastward expansion.
The Ukraine government has alleged that Moscow could be planning a military invasion of the nation by the end of January and said it has amassed 94,000 Russian troops along the border in the second such buildup so far this year.
“I indicated that ... in fact we would probably be required to reinforce our presence in Nato countries ... and in addition to that I made it clear that we would provide defence capabilities to Ukraine,” Mr Biden said, adding that he is confident that the Russian president got the message.
Briefing reporters about his talks with US counterpart, Mr Putin said: "We agreed we will continue this discussion and we’ll do it in a substantive way. We will exchange our ideas in the very near future. Russia will draw up its ideas literally in the coming days, within a week we will give this to the US side to consider.”
He said it was "provocative" to throw the question at Moscow whether Russia planned to attack Ukraine and accused NATO of threatening Russia’s security.
The US has not revealed what economic measures it might take against Russia. But US National Security Adviser Jake Sullivan hinted at Nord Stream 2, a new gas pipeline project from Russia to Germany, which is at the heart of controversy after some reports said the US reached an agreement with Germany to shut down the project in case of invasion.
The gas pipeline is not yet functional but Mr Sullivan noted that provided it "leverage" for the US and its allies. "If Vladimir Putin wants to see gas flow through that pipeline, he may not want to take the risk of invading Ukraine," he told reporters
Meanwhile, Ukrainian president Volodymyr Zelenskyy’s chief of staff expressed gratitude to the US president for his “unwavering support.”
