WASHINGTON -- In his most direct attack to date on the Republicans vying for his job, President Barack Obama on Tuesday knocked his GOP challengers for their "casualness" in talking about the prospect of going to war with Iran, suggesting that their tough talk is devoid of any real substance.

During a White House press conference, Obama said there is still time for dealing diplomatically with Iran as the country signals it may be trying to develop a nuclear weapon. That is the view of U.S. and Israeli intelligence officials, he said, and as such, he said he plans to keep working with the international community to impose sanctions on Iran.

Then, without naming names, the president slammed Republican presidential candidates Mitt Romney and Rick Santorum, who have criticized him for being too passive on Iran by not endorsing military action.

"What's said on the campaign trail, you know, those folks don't have a lot of responsibilities. They're not commander-in-chief," Obama said. "When I see the casualness with which some of these folks talk about war, I'm reminded of the costs involved in war. I'm reminded of the decision that I have to make, in terms of sending our young men and women into battle, and the impacts that has on their lives, the impact it has on our national security, the impact it has on our economy."

"This is not a game, and there's nothing casual about it."

Taking it a step further, Obama said Republicans who are "beating the drums of war" should have to explain clearly to the American people what they think the costs and benefits would be to going to war with Iran. "They should explain to the American people exactly why they would do that and what the consequences would be," he said. "Everything else is just talk."

When pressed for specifics on how to respond to Iran, the president suggested there is some irony in the fact that, for all their "bluster" and "big talk," his Republican challengers end up repeating Obama's policies from the past few years.

"It indicates to me that [their criticisms are] more about politics than actually trying to solve a difficult problem," he said.

Obama's press conference coincidentally -- or not so much -- lands on the same day as Super Tuesday, which could decide once and for all who the Republican presidential nominee will be. The president declined to call out any of his challengers by name, but asked if he had any response to Romney's characterization of him as "feckless," Obama had a message for the GOP hopeful.

"Good luck tonight," he said to laughs. "No, really."

UPDATE: 3:30 p.m. -- Asked at a Capitol Hill press conference about Obama's suggestion that some of the comments that appeared to favor war were politically motivated, Senate Minority Leader Mitch McConnell (R-Ky.) said the issue is the threat that Iran poses.

"I'm a lot more concerned about nuclear proliferation in the Middle East," McConnell said. "In what way would kicking the can down the road and allowing Iran to become the possessor of a nuclear weapon and the ability to deliver them -- in what way does that make us a safer world?"

McConnell has proposed having the Senate pass a resolution to use military force against Iran if Tehran starts enriching uranium to weapons grade. He said that was not necessarily a call to war.

"A resolution authorizing the use of force is not a mandate to use force, but clearly would indicate to the Iranians that we're willing to go beyond sanctions that many of us are skeptical are likely to get the final result," McConnell said.

Senate Majority Leader Harry Reid (D-Nev.) countered minutes later by echoing the president and cautioning that lawmakers should leave the matter to Obama.

"I'm not going to be part of rushing forward on a declaration of war. These are things that have to be done very, very cautiously. We have problems around this world that are so significant," Reid said. "Let's just stop throwing the word 'war' around so casually."