Ukraine's opposition is accusing Russia of 'aggression' in Crimea and says it will defend its independence.
Meanwhile, Russian President Vladimir Putin says he wants to find a 'diplomatic solution' to the crisis in Ukraine.
In a phone call, Britain's David Cameron and Germany's Angela Merkel urged him to 'de-escalate' the situation in Crimea.
Putin also said he believes the government of Crimea is legitimate, as it plans a referendum on breaking away from Ukraine.
Ukraine's prime minister has confirmed he will travel to the US for top level talks about the Crimea crisis.
The US Secretary of State John Kerry has told the Russian Foreign Minister that any moves to annex Crimea would close the door to diplomacy.
President Obama and European leaders have agreed there's still a way for President Putin to resolve the situation peacefully.
Ukrainian opposition leader Vitali Klitschko is accusing Russia of over aggression:
