US Official: Russian Forces Have "Complete" Control of Crimea, Ukraine

WASHINGTON, DC (CNN) - Russian forces now "have complete operational control of the Crimean Peninsula," a senior U.S. administration official said Sunday of the escalating crisis in Ukraine.

The United States estimates there are 6,000 Russian ground and naval forces in the region, the official said. Amid the tensions, U.S. Secretary of State John Kerry will travel to Kiev on Tuesday, an Obama administration official said.