One U.S. official says Vladimir Putin's willingness to use force in Ukraine should not be underestimated.
Republican Representative Mike Rogers of Michigan told ABC's "This Week" Putin will do whatever it takes to reassert Russian control in Ukraine and Crimea.
He says Putin wants to be back on the world stage and if he has to use brute force to do it, he will.
Rogers, who chairs the House Intelligence Committee, also says Putin should not be underestimated.
European monitors have been barred from entering the Crimean peninsula and Russian troops have reportedly surrounded Ukrainian military bases.