15 OSCE nations, including the US, agree to send military observer mission to Ukraine.

A U.S. official says the Organization for Security and Cooperation in Europe will send a military observer mission to Ukraine at its request.

Daniel Baer, the chief U.S. representative to the OSCE, said 15 of its nations, including the United States, decided in Vienna on Tuesday to volunteer members for the mission, which Ukraine had asked for. He said it will head to Ukraine as early as Wednesday, with the goal of then traveling to Crimea.

On Saturday, heavily armed pro-Russian forces took over the strategic peninsula in Ukraine, surrounding its ferry, military bases and border posts. Two Ukrainian warships remained anchored in the Crimean port of Sevastopol, blocked from leaving by Russian ships.

The U.S. is preparing economic sanctions against Russia amid worries that Moscow is ready to stretch its military reach further into the mainland of the former Soviet republic.

The OSCE includes Russia, the United States, and all European countries.