US President Barack Obama has offered a mischievous "good luck tonight" to his possible 2012 White House foe Mitt Romney as the Republican awaited his fate in Super Tuesday nominating clashes.
Obama was asked by a reporter to respond to Romney's claims that he is the most "feckless" president since Jimmy Carter in the 1970s and thought "hope" would do as a foreign policy when facing down Iran's nuclear challenge.
"Good luck tonight," Obama laughed in response, prompting another reporter at the news conference to ask "Really?"
"Really," a beaming Obama replied, choosing to keep a personal clash for the future, should the former Massachusetts governor confirm his front-runner status and finally emerge as the Republican presidential nominee.
Obama did however have harsh words for Republican candidates who he said were guilty of "big talk" and "bluster" over possible military action against Iran's nuclear program without considering the costs of such a move.
"If some of these folks think that it's time to launch a war, they should say so," Obama said.
"They should explain to the American people exactly why they would do that and what the consequences would be. Everything else is just talk.
"You know, those folks don't have a lot of responsibilities. They're not commander in chief."
Obama held a news conference in an apparent bid to steal some of the limelight from Republican candidates contesting 10 states in the crucial Super Tuesday nominating contests.