U.S. President Joe Biden has said the United States will not send troops to Ukraine to defend against any potential Russian invasion.
Biden spoke to reporters on December 7, a day after he and his Russian counterpart, Vladimir Putin, held a two-hour videoconference.
Biden said he had warned Putin that if Russia did launch new military action against Ukraine -- something U.S. intelligence has warned might be possible in the coming weeks -- the United States and allies would impose sanctions "like none he'd ever seen."
"The idea the United States is going to unilaterally use force to confront Russia invading Ukraine is not in the cards right now," he also said, according to a White House transcript.
"We have a moral obligation and a legal obligation to our NATO allies under Article 5. It's a sacred obligation. That obligation does not extend to...Ukraine," which is not a member of the military alliance, Biden said.
Washington has signaled it plans to supply more weaponry, including Javelin anti-tank missiles, and other materiel to Ukraine.
Tens of thousands of Russian troops have deployed to regions near the Ukrainian border, alarming both Ukraine and officials in Europe and the United States.
In his own comments describing the conference call with Biden, Putin again repeated Russia's insistence that Ukraine should never be allowed to join NATO.
"We cannot fail to be concerned about the prospect of Ukraine's possible admission to NATO, because this will undoubtedly be followed by the deployment there of military contingents, bases and weapons that threaten us," the Russian president said.