President Barack Obama told Russian President Vladimir Putin on Sunday that Crimea’s vote to secede from Ukraine and join Russia would never be recognized by the United States.
The two leaders spoke after residents in Crimea voted overwhelmingly in favor of the split.
The White House said Obama told Putin the Crimean vote violates the Ukrainian constitution and occurred under duress of Russian military intervention.
He also said the U.S. was prepared to impose retaliatory penalties on Russia.
Obama urged Putin to work with Ukraine as well as Western nations to resolve the crisis diplomatically.