WASHINGTON — Republican White House hopeful Mitt Romney stood firm Tuesday in painting Russia as a key geopolitical foe, warning that Moscow pursues policies that are "antithetical" to US interests.

"Of course we're not enemies. We're not fighting each other, there's no Cold War," Romney told Fox Radio in an interview aired on the final day of his bus tour through six swing states.

"But Russia is a geopolitical opponent, and in that regard I think we've seen very clearly that they continue to pursue a course which is antithetical to the interests of our nation."

He described Russia, where Vladimir Putin recently assumed the presidency for a third term, as "the nation which consistently opposes our actions at the United Nations."

And Romney said US President Barack Obama, whom he is challenging in November's election, has been only too happy to provide Moscow what it's wanted since the Democrat entered the White House in early 2009: "a reset policy of giving Russia a withdrawal of our missile defense sites from Eastern Europe."

Romney described the reset as "an enormous mistake" which merely showed "an enormous naivety of a presidency that does not understand the power of resolve and strength."

The Republican flagbearer caused a diplomatic spat in March when he accused Moscow of being America's "number one geopolitical foe" -- raising eyebrows from critics who say that honor belongs to Al Qaeda, North Korea or Iran.

Russia's then-president Dmitry Medvedev shot back that presidents should "use their head" when formulating their positions, adding that "it is now 2012, not the mid-1970s."

Romney's radio comments followed a cordial but formal meeting Monday between Obama and Putin at the G20 summit in Mexico, where they agreed on the need for a viable political process in Syria but could not frame an immediate plan to end the bloodshed there.

The hawkish stance on Russia by Romney, a former governor of Massachusetts, has been criticized by Democrats and perplexed some Republicans, including former secretary of state Colin Powell, who has rebuked the presumptive nominee for his comments.

Romney's bus tour wrapped up Tuesday in his native Michigan, where he campaigned in Frankenmuth and attacked Obama's policies as harmful for the country.

"I've looked at what he's done and I haven't heard anyone say thank goodness for Barack Obama's policies," Romney said, according to the Detroit Free Press.

"He's making it harder for Frankenmuth, central Michigan, and the nation."