Mitt Romney, former Massachusetts governor and a possible head of the White House, called Russia the main geopolitical main enemy of the United States. He made the statement during his appearance on CNN.
"Russia, this is, without question, our number one geopolitical foe. They - they fight every cause for the world's worst actors," he said, commenting on the outcome of the meeting of the US and Russian presidents in Seoul.
During a conversation about missile defense, Obama told his Russian counterpart 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.
"Russia - Unfriendly figure on the world stage. Fact that the president is seeking greater flexibility in relations with Russia despite the fact that he had nothing to say to the American people about the relationship with Russia - a very disturbing sign. I am very, very concerned about this. It - Russia is, without question, our geopolitical enemy number one "- said Romney.
Romney takes the lead on the number of delegates, who in a few months will vote for him at the Republican Convention, which would formally define a rival to Barack Obama at the presidential election in November.