A State Department spokesperson said Secretary of State Antony Blinken told a European official that it was "important to support Ukraine's territorial integrity" and that "any new Russian aggression" will lead to a harsh response.

A senior US administration official said on Saturday that the United States and its allies are ready to discuss with Russia, during talks on Ukraine, the possibility of the two sides placing limits on military exercises and missile deployments in the region.

The round of talks is scheduled to start in Geneva on Sunday, but the official said the United States "is not ready to discuss restrictions on the deployment of US forces or the status of these forces in NATO countries in the region."

US President Joe Biden warned that Russia would face "serious economic consequences" if his Russian counterpart, Vladimir Putin, decided to "invade Ukraine". On Saturday, US officials provided more details about the severe sanctions that could be imposed.

Possible sanctions on Russia

A source familiar with the possible sanctions said one of these restrictions could target important Russian industrial sectors, including defense and civil aviation, and would affect Russia's ambitions in high-tech fields such as artificial intelligence.

The Geneva talks, to be followed by other rounds next week in Brussels and Vienna, aim to avoid a crisis. Russia wants security guarantees and an end to NATO's eastward expansion, demands the United States says are unacceptable.

Russia says it feels threatened by the prospect of the United States deploying offensive missile systems in Ukraine, but Biden claimed that he has no intention of doing so.

The source added that the United States is discussing with allies and partners in Europe and Asia imposing trade restrictions on Russia.