Bedford, N.H. ? Continuing a nasty dispute over negative campaign tactics, Mitt Romney said Wednesday that if Newt Gingrich can’t take the heat generated by attack ads during the GOP presidential primary, he’ll wilt going up against President Barack Obama.

Appearing on morning television programs, Romney responded to Gingrich’s claims that a special political action committee that supports Romney is running misleading and false ads against the former House speaker that have taken a toll on his campaign.

Gingrich has called on Romney to urge his allies to stop the advertising onslaught, a demand the former Massachusetts governor has dismissed as they both vie for Iowa and New Hampshire voters who will begin rendering judgment in less than two weeks.

Romney said he can’t control what the independent PAC does and needled Gingrich as being too thin-skinned for a drawn-out contest against Obama.

“There are limits to what you can tell a PAC,” Romney said Wednesday on Fox News Channel. “I’m sure I could go out and say, ‘Please, don’t do anything negative.’ But this is politics. And if you can’t stand the heat in this little kitchen, wait until the Obama’s Hell’s Kitchen turns up the heat.”

In subsequent interview on MSNBC that touched on foreign affairs, Romney said he would not rule out military “support” to oust Syrian President Bashar Assad, who has overseen a deadly nine-month uprising against his regime. Romney said as recently as last month that the time had come for Assad’s regime to end.

The spat over attack ads has dominated the GOP campaign in recent days as Gingrich, picking up endorsements from legislative leaders in Iowa and New Hampshire, and Romney, on a bus tour of New Hampshire, worked to fit in as much glad-handing with voters as possible before taking a break for Christmas.

“I don’t object to being outspent. I object to lies. I object to negative smear campaigns,” Gingrich said Tuesday, suggesting that Romney was being less than truthful when he claimed he can’t do anything about hard-hitting spots coming from the independent group, Restore Our Future, formed by staffers from his 2008 campaign. “Understand, these are his people running his ads, doing his dirty work while he pretends to be above it.”

“I think these guys hire consultants who get drunk, sit around and write stupid ads,” a fired-up Gingrich said. “Every one of these candidates should take responsibility for the lies they are putting up.”

Earlier Tuesday, Romney said in an appearance on MSNBC that these political action committees have been “a disaster.” But he refused to urge the group backing him to halt its attacks on Gingrich, citing federal law that prohibits coordination between his campaign and such groups. And he pointedly declined to disavow the ads.

“I’m not allowed to communicate with a super PAC in any way, shape or form,” Romney said. “If we coordinate in any way whatsoever, we go to the big house.”

Hours later, Gingrich read Romney’s remarks to reporters and then promptly labeled them “baloney.” Said Gingrich, “His comments are palpably misleading, clearly false and are politics at its worst form.”

The standoff over negative ads comes as Gingrich has lost ground in Iowa and elsewhere after the Romney-aligned super PAC and others, including Texas Rep. Ron Paul, have blanketed the airwaves with ads casting Gingrich as a Washington insider who profited on his name after leaving office. The ads have knocked Gingrich off message just as he’s seeking to make his closing argument to Iowa voters ahead of the Jan. 3 caucuses.

With Gingrich flailing, Romney focused on Obama in a speech Tuesday in which he accused Obama of deepening the economic crisis and backing policies that will redistribute wealth instead of creating equal opportunity for people to do well.

Polls show Romney, Gingrich and Paul in contention for the lead in Iowa and elsewhere.

Paul, the blunt-spoken Texas congressman, was campaigning Wednesday in Iowa, along with other candidates in the field. The race there remains unpredictable, as voters weigh electability against conservative credentials.

Jenny Turner, a 31-year-old wedding videographer from Mount Pleasant, Iowa, summed it up this way: “My heart is with Newt. But Mitt Romney is in the back of my mind.”

The bickering over negative ads has highlighted the role of so-called super PACs, independent groups that may accept unlimited donations but are not supposed to directly coordinate with candidates. Such groups have sprung up to work on behalf of every serious Republican candidate after a U.S. Supreme Court decision last year that allowed individuals, unions and corporations to donate unlimited sums of money to outfits advocating the election or defeat of candidates.

On Tuesday, Gingrich and Romney decried the system, with Romney calling it a “disaster” and Gingrich branding it as a “nightmare.” But both benefit from super PACs.

Two pro-Gingrich groups have started raising money, and Gingrich’s longtime aide Rick Tyler just signed on with one of them.

Romney’s supporters, however, have had a yearlong head start in raising money. Restore Our Future is slated to spend roughly $3 million on ads, most of which paint Gingrich as an ethically-challenged Washington power broker.

Gingrich, who trails Romney badly in fundraising after a campaign implosion this year, said he would disavow any group that runs negative ads on his behalf.

In a sign of his fundraising and organizational deficiencies, Gingrich was rushing later Wednesday to Virginia, the state the former Georgia congressman now calls home, to help ensure he has the needed signatures to get on the ballot there.

Hunt reported from New Hampshire.