He said Mr. Putin will only be swayed by economic consequences of sanctions on his country and Russian mothers saying, "What is happening here?" when troops come back from Ukraine in body bags.
Sen. Robert Menendez: Russia has launched a direct attack on Ukraine →
"This is a direct invasion by Russia," he told CNN's "State of the Union." "It's not rebels, it's Russian soldiers."
Obama seeks to reassure jittery NATO members after Russia's invasion of Ukraine →