U.S. President Barack Obama says there will be costs for any Russian military intervention in Ukraine.
In a brief statement to reporters at the White House Friday, the president said any violation of Ukrainian sovereignty by Russia would be deeply destabilizing.
He said the United States is deeply concerned by reports of Russian military movements in Crimea. Mr. Obama said he wants to make it very clear that the Ukrainian people deserve the opportunity to determine their own future. He reminded Russia that it has committed itself to respect Ukrainian sovereignty.
Before the president spoke, Ukraine's United Nations ambassador, Yuriy Sergeyev, told an emergency Security Council meeting that Russian attack helicopters and military transport planes have crossed into Crimea.
He described the main airport as being "captured" by Russian forces. Sergeyev said he wants moral and political support from the world community and that what is going on in his country is "awful."
U.S. Ambassador Samantha Power said the United States is calling for an urgent international mediation mission for Crimea.
Russian ambassador Vitaly Churkin says his country is against what he calls externally imposed mediation.
When asked whether Russia has invaded Ukraine, he said Russia is acting within a treaty with Ukraine that allows it to have a base in Crimea for the Russian Black Sea fleet.