The US has condemned Russian President Vladimir Putin's attempt to formally annex Ukraine's Crimea region, calling it "a threat to international peace and security" and "against international law".
White House Press Secretary Jay Carney told reporters: "We condemn Russia's moves to formally annex the Crimean region of Ukraine.
"We would not recognise this attempted annexation. As we have said, there are costs for such action".
An unusually frank Nato Secretary General issued an unequivocal warning on the course of events should Russia attack Latvia or Estonia.
The West responds with sanctions and closer political ties with Ukraine as Russia's President seals the annexing of Crimea to much fanfare.
Supporters of the controversial fracking industry believe shale gas could be America's most potent weapon in the stand-off with Russia.