SAN DIEGO - Mitt Romney said today that Russia - not Iran or North Korea - is the United States' "number one geopolitical foe," adding that Russia "always stands up for the world's worst actors."

Romney's remarks came during an interview with CNN's Wolf Blitzer, during which he spoke about the comments made by President Obama early today that were caught by an open microphone. During a conversation about missile defense, Obama told Russian President Dmitri Medvedev that he'd have more "flexibility" after the election.

Romney said he was "very concerned" about the president's remarks, especially because they were made to a Russian leader.

"Russia is not a friendly character on the world stage and for this president to be looking for greater flexibility where he doesn't have to answer to the American people in his relations with Russia is very, very troubling, very alarming," he said. "I am very, very concerned.

"This is to Russia," Romney said. "This is without question our number one geopolitical foe.

"They fight every cause for the world's worst actors. The idea that he has more flexibility in mind for Russia is very, very troubling indeed," he said.

When pressed by Blitzer as to whether he truly believed Russia was a bigger foe than Iran or China, Romney sought to clarify his remarks, but did not back away from his argument.

"I'm saying in terms of a geopolitical opponent, the nation that lines up with the world's worst actors, of course the greatest threat that the world faces is a nuclear Iran, and nuclear North Korea is already troubling enough, but when these terrible actors pursue their course in the world and we go to the United Nations looking for ways to stop them, when [Syrian President] Assad, for instance, is murdering his own people, we go to the United Nations and who is it that always stands up for the world's worst actors?" Romney asked.

"It is always Russia, typically with China alongside, and so in terms of a geopolitical foe, a nation that's on the Security Council, that has the heft of the Security Council, and is of course a massive security power - Russia is the geopolitical foe and the idea that our president is planning on doing something with them that he's not willing to tell the American people before the election is something that I find very, very alarming," he said.