Sen. John McCain returned from a trip to Ukraine on Sunday, calling for "a fundamental re-assessment" of the United States' relationship with Russian Vladimir Putin.

“No more reset buttons," McCain told Candy Crowley on CNN's "State of the Union." “No more reset buttons, no more ‘Tell Vladimir I’ll be more flexible.’ Treat him for what he is. That does not mean re-ignition of the Cold War. But it does mean treating him in the way that we understand an individual who believes in restoring the old Russian empire.”

McCain, who has been critical of the Obama administration's response to the crisis in Crimea, said the White House should target Russia's oil exports.

"Russia is a gas station masquerading as a country,” McCain said. “It’s kleptocracy, it’s corruption. It’s a nation that’s really only dependent upon oil and gas for their economy. And so economic sanctions are important. Get some military assistance to Ukrainians, at least so they can defend themselves. Resume the missile defense system in Poland and the Czech Republic. Look at Moldova and Georgia, both of whom are occupied by Russian troops as we speak, a path toward membership in NATO.”

Speaking in Kiev with a delegation of fellow U.S. senators on Saturday, McCain called for the United States to provide long-term military support — both "lethal and non-lethal" equipment — to Ukraine. "[It is] the right and decent thing to do," McCain said.

In a New York Times op-ed published Saturday, the Republican senator sharpened his criticism of the president.

"Crimea has exposed the disturbing lack of realism that has characterized our foreign policy under President Obama," McCain wrote. "It is this worldview, or lack of one, that must change."

McCain added: "Crimea must be the place where President Obama recognizes this reality and begins to restore the credibility of the United States as a world leader."

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