President Obama today rebuffed criticisms that he has been weak on Iran, accusing the Republicans vying to challenge him in the fall of "beating the drums of war" amid rising concerns about the prospect of Iran developing a nuclear weapon.

"What's said on the campaign trail, you know, those folks don't have a lot of responsibilities," the president said at his first White House news conference of the year. "They're not commander in chief."

The president warned that critics of his Iran policy, "folks who have a lot of bluster and a lot of big talk," are neglecting the true costs of war.

"This is not a game.  And there's nothing casual about it," the president said. "We don't play politics with it. When we have in the past, when we haven't thought it through and it gets wrapped up in politics, we make mistakes."

Republican presidential frontrunner Mitt Romney has accused the Obama administration of having "dawdled" with sanctions against Iran.

"As president, I will be ready to engage in diplomacy. But I will be just as ready to engage our military might. Israel will know that America stands at its side, in all conditions and in all consequence," Romney told the American Israel Public Affairs Committee Policy Conference today.

The president portrayed such remarks as dangerous political posturing.

"I think there's no doubt that those who are suggesting or proposing or beating the drums of war should explain clearly to the American people what they think the costs and benefits would be.  I'm not one of those people," he said.

The "Super Tuesday" news conference gave the president a chance to divert attention away from the Republican presidential candidates, who are facing off in 10 contests today.

When asked to respond to Romney's accusations about his foreign policy, Obama simply wished Romney "good luck tonight."

"No, really?" one reporter asked.

"Really," Obama responded, to laughter from the White House press corps.

The president continued to argue that, when it comes to preventing Iran from obtaining a nuclear weapon,  there is still a "window of opportunity" for diplomatic and economic pressures to work.

Notably absent from the president's remarks, however, were his recent calls for all options, including military action, to be on the table.

Obama's continued push for diplomacy comes as the Israelis have asked the White House to more starkly threaten military action against Iran if it continues to violate its international agreements to refrain from building a nuclear weapon.

Obama assured Israeli Prime Minister Benjamin Netanyahu Monday that "the United States will always have Israel's back when it comes to Israel's security." The president said today he was simply restating his "consistent position that the security of Israel is something I deeply care about."

"It was not a military doctrine that we were laying out for any particular military action," Obama said.