U.S. President Barack Obama said the proposed Crimea referendum violates international law and the Ukraine constitution during a speech at the White House on Thusday.
Earlier on Thursday, Crimea's Moscow-backed parliament voted to allow the southern Ukrainian region to become part of Russia, as the U.S. ordered asset freezes and travel bans on a list of individuals it said were involved in Russia's military intervention.
"These decisions continue our efforts to impose a cost on Russia and those responsible for the situation in Crimea," Obama said, adding that he's pleased with what he described as "international unity."
"I am confident that we are moving forward together—united in our determination to oppose actions that violate international law and to support the government and people of Ukraine," he added.
As part of a path of deescalation of the crisis, Obama said Russia should let international monitors into Ukraine. He also called on Congress to support the International Monetary Fund's capacity to lend resources to Ukraine and to provide American assistance to the Ukraine government.
"Today, the world can see that the United States is united with our partners and allies in upholding international law and pursuing a just outcome that advances global security in the future that the Ukraine people deserve," Obama said.
—CNBC.com with Reuters