Dispute between the United States and Russia has entered a new phase following the secession referendum in Crimea.
Crimea has made an official request to join Russia.
On March 16, nearly 97 percent of the people in Crimea voted in favor of breaking away from Ukraine and joining Russia.
The United States and the European Union, which support the new Ukrainian government, have rejected the vote as "illegal."
Russia, however, says the referendum is legal and complies with international law.
On Monday, US President Barack Obama issued an executive order that imposes sanctions on 11 Russian, Crimean, and Ukrainian individuals for "contributing to the situation in Ukraine."
Russia’s Upper House speaker has described the sanctions as "unprecedented political blackmail".
Russia says it is ready to cooperate with the West on Ukraine if the country adopts a federal constitution and accepts Crimea’s secession.