WASHINGTON (AP) — 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, as he and other top U.S. officials warned Moscow against making further military moves toward southern and eastern Ukraine.

The two leaders spoke after residents in Crimea voted overwhelmingly in favor of the split in a referendum that the United States, European Union and others say violates the Ukrainian constitution and international law and took place in the strategic peninsula under duress of Russian military intervention. Putin maintained that the vote was legal and consistent with the right of self-determination, according to the Kremlin. But the White House said Obama reminded Putin that the U.S. and its allies in Europe would impose sanctions against Russia should it annex Crimea. U.S. and EU sanctions are expected to be announced Monday.