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(CNN) – A defiant Russian President Vladimir Putin denied having designs on seizing Ukraine's Crimean peninsula, while defending his country's right to intervene to protect ethnic Russians and others he said were under threat.
"I'm not worried that a war will start, because we're not going to go to war with Ukraine," he said. "I want you to understand clearly: If we do this, it will only be to protect local people."
But on the ground, the Russian siege of Ukrainian military facilities continued.
"It's going to be very difficult to get the Russians out of Crimea," said Sen. Bob Corker, ranking member of the Senate Foreign Relations Committee.
Even before the invasion, Russians already had a major naval presence in Crimea, which is located in the southern part of Ukraine.
"Our efforts right now should be to keep them from advancing any more into eastern Ukraine," Corker told CNN's "The Lead with Jake Tapper."
U.S. Secretary of State John Kerry accused Russia of making up reasons to intervene in Ukraine, saying Tuesday that "not a single piece of credible evidence" supports Russian explanations for its move into Crimea.
But Russia has a history of such behavior, says Corker.
"Putin has learned that this has worked for him in the past. It worked in Georgia just a few years ago, and he's done similar kinds of things in Maldova. And I think this is the way he acts when he feels his interests are threatened," said Corker.
For more of our interview with Sen. Bob Corker, check out the video above.