In a travel alert issued on Friday, the State Department also advised Americans in Russia to be aware of the heightened military presence and ongoing military exercises of troops along the border region with Ukraine.

The Department said that US citizens considering travel to Russia should evaluate their personal security in light of political tensions and the possibility of violence or anti-US actions directed against Americans or US interests.

US officials also advised Americans to avoid all public demonstrations and any large crowds and public gatherings that lack enhanced security measures.

The United States and Russia failed Friday to resolve a Cold-War-style standoff sparked by intervention in Ukraine and especially in Crimea region, as the clock ticks down to the region's vote on splitting from Ukraine.

US Secretary of State John Kerry warned against the Russian parliament or Duma ratifying Sunday's vote, insisting that the move would trigger US-led sanctions and escalate the biggest East-West showdown since the 1989 fall of the Berlin Wall.

Russian Foreign Minister Sergei Lavrov hinted after a Friday meeting with Kerry that Moscow was now resolved to bring Crimea under its eventual control.

"Everyone understands -- and I say this with all responsibility -- what Crimea means to Russia, and that it means immeasurably more than the Comoros (archipelago) for France or the Falklands for Britain."

NTJ/MB