The White House says it rejects Crimea's referendum on seceding from Ukraine, saying the Sunday vote has been influenced by "threats of violence and intimidation" by Russia.
"This referendum is contrary to Ukraine's constitution, and the international community will not recognize the results of a poll administered under threats of violence and intimidation from a Russian military intervention that violates international law," White House spokesman Jay Carney said in a statement.
Carney said that Russia's actions in the region will "bring increasing costs" from the United States and its allies.
"As the United States and our allies have made clear, military intervention and violation of international law will bring increasing costs for Russia - not only due to measures imposed by the United States and our allies but also as a direct result of Russia's own destabilizing actions," he said.
Earlier on Sunday, Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov in a telephone conversation that the United States would not accept the results of the referendum.