The U.N. Security Council in New York will hold an urgent meeting on Saturday after the Russian parliament approved President Vladimir Putin's proposal to send troops into Ukraine, council delegations said.
Britain's Foreign Secretary William Hague said he is "deeply concerned" by Russian's potential military maneuvers and said he spoke with Russian Foreign Minister Sergey Lavrov to urge him to "calm this dangerous situation."
Hague also made the rounds with other foreign officials. In a tweet, he said he spoke to German Foreign Minister Frank-Walter Steinmeier and discussed the need for international diplomatic action to address the crisis.
He also spoke with acting Ukrainian President Oleksandr Turchynov, and said he assured his country's commitment to Ukraine.
Meanwhile, a U.S. administration official said the U.S. was "considering the potential costs" that President Barack Obama outlined Friday when he warned Russia not to intervene militarily in Ukraine.
The United Nations Security Council meeting will take place at 2 p.m. ET. Russia is a permanent member of the 15-nation Security Council, and therefore, is able to veto any actions proposed by its members.
Reuters contributed to this report.