President Obama on Tuesday defended his approach to dealing with Russian President Vladimir Putin, calling Russia a "regional power” and standing behind his dismissal of presidential rival Mitt Romney's assertion that the Kremlin posed a major threat to U.S. interests.

"Russia's actions are a problem,” Obama said during a press conference in the Netherlands during a nuclear summit with world leaders. "They don't pose the No. 1 national security threat to the United States. I continue to be much more concerned when it comes to our security, with the prospect of a nuclear weapon going off in Manhattan.”

Obama's presidential campaign roundly mocked Romney's views on Russia, attacks that have now come under fire in the wake of Putin swiftly annexing Crimea and raising concerns about an extended Kremlin power grab in Ukraine.

Facing questions about whether Romney had a point, Obama said he was under no “illusion” about the Russian president’s goals but was less concerned about Putin's motivations than finding a solution to the crisis.

“The truth of the matter is that America’s got a whole lot of challenges,” Obama said from The Hague. “Russia is a regional power that is threatening some of its immediate neighbors, not out of strength but out of weakness.”

The Obama administration and its European allies on Monday essentially kicked Russia out of the Group of Eight nations and threatened to impose stiff sanctions on individual sectors of the Russian economy if Putin further stoked tensions in Ukraine.

However, the lack of concrete sanctions raised questions over whether the White House had conceded that Crimea would remain under Russian control.

"I think it’d be dishonest to suggest there’s a simple solution to resolving what has already taken place in Crimea," Obama admitted.

But he insisted that the Russian takeover of Crimea was not a “done deal.”

Still, critics have accused the White House of not doing enough to deter Putin from turning his attention to areas of Ukraine beyond Crimea, or loosening his grip on the disputed peninsula.

Driving the White House’s reluctance to wield a hammer against Putin is that wide-ranging economic sanctions would carry major consequences for Europe, which is heavily reliant on Russian goods and services.

“Should Russia go further, such sectoral sanctions would be appropriate,” Obama pledged on Tuesday.

"He just has to understand there is a choice to be made here,” Obama added of Putin.