Russia is capable, if it wants, of pulling twice as many forces to Ukraine as it did last spring, U.S. Undersecretary of State Victoria Nuland said.

"If we fully mobilize the forces that are planned to be used for this purpose, the military grouping will be twice as large as it was last spring. Specifically, we're talking about about 100 battalion tactical groups, in other words, about half of Russia's ground forces based west of the Urals," Nuland said in a statement to the U.S. Senate Foreign Affairs Committee.

Nuland added that the U.S. estimates that Russia "has deployed nearly 100,000 troops near Ukraine's northern, eastern, and southern borders.

These forces, according to the deputy secretary of state, "continue to prepare for decisive action in Ukraine if ordered to do so. This is potentially possible in early 2022.