US President Barack Obama held a second Ukraine-focused meeting of the National Security Council in two days.
Mr Obama met with the council for more than two hours on Monday evening and again on Tuesday morning to discuss steps the US can take to de-escalate the crisis in Crimea.
He said that Russia's legitimate interests in Ukraine did not give it a right to "use force as a means of exerting influence", and insisted the Ukrainian people should be able to decide their own future.
Russian president Vladimir Putin said he would only use force in Ukraine as a "last resort" as he defended Russia's actions in Crimea.
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