Former secretary of defense Robert Gates predicted Sunday that any hope of Ukraine holding on to control of Crimea is gone and that Russia will seize control of the area.

"I do not believe that Crimea will slip out of Russia's hands," he said on "Fox News Sunday."

You think Crimea's gone?" asked host Chris Wallace.

"I do," responded Gates.

As Russian forces have tightened their grip over the region, Crimea has set a referendum for next Sunday to decide whether to join Russia. The United States has said it will not recognize such a move.

Gates said "there really aren't any direct military options" for the U.S. with regard to the situation in Ukraine.