UN Secretary-General Ban Ki-moon has said tension between Ukraine and Russia poses "great risks to the countries themselves and beyond" following a meeting with President Putin.
"I have emphasised that all parties (should) refrain from any hasty or provocative actions that could further exacerbate the already very tense and very volatile situation," Ban said.
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.