McCain added that President Obama and his staff have been naive about Putin, whose forces have occupied neighboring Crimea.
"I don't know when the President and his advisers will wake up to what Putin is all about. We've got to start with the fundamental reassessment of our relationship with him," he said.
Obama's decision to impose sanctions made him "less optimistic" about U.S. ability to limit Russia's aggression in eastern Ukraine, Mccain said, and he urged the President to consider a tougher response to Putin.
"He should have said we're going to provide military assistance to Ukraine, but to not do that after this country has lost a large part of its territory due to Russian aggression," he said.