Ten Republican presidential hopefuls battled for bragging rights as toughest on the war on terror, in their hawkish second campaign debate on the long road to the White House.
Former New York mayor Rudolph Giuliani meanwhile leapt onto the attack against his rivals, after taking a pounding over his equivocal position on abortion rights in their first showdown two weeks ago.
Candidates also savaged rival Democrats over their attempts to bring home troops from Iraq, and traded charges over who was most conservative on cutting taxes, social issues and immigration.
At one stage in Wednesday's debate, Giuliani flashed with anger, after longshot candidate Congressman Ron Paul appeared to suggest US foreign policy invited the September 11 attacks in 2001.
"That's an extraordinary statement, as someone who lived through the attack of September 11, that we invited the attack because we were attacking Iraq," Giuliani said.
"I don't think I've ever heard that before, and I've heard some pretty absurd explanations for September 11," he said, demanding Paul withdraw the comment, and reflecting the signature role his praised leadership in New York on September 11 is playing in his campaign.
Former Massachusetts Governor Mitt Romney, who many observers say won the first Republican debate, also took a tough line.
"Some people have said we ought to close Guantanamo. We should double Guantanamo," he said, referring to the controversial 'war on terror' camp in Cuba.
Candidates were asked how they would respond to a terror attack in which suicide bombers had left hundreds dead at shopping centers, and how they would interrogate suspected accomplices of the killers.
"I would tell the people who had to do the interrogation to use every method they could think of," said Giuliani.
"Shouldn't be torture, but every method they can think of."
But Senator John McCain, a former Vietnam prisoner of war who has clashed with the Bush administration on interrogation techniques, warned "we could never gain as much we would gain from that torture as we lose in world opinion."
"The more physical pain you inflict on someone, the more they're going to tell you what they think you want to know."
Giuliani's rivals skewered him over abortion following his earlier comments on an issue that is an act of faith for many core anti-abortion Republicans.
"I ultimately do believe in a woman's right of choice, but I think that there are ways in which we can reduce abortions," he said.
Former Arkansas governor Mike Huckabee damned Giuliani with faint praise over abortion, which many experts believe will make it tough for the former mayor to win the Republican nomination.
"He's been honest about his opinion ... but I'm pro-life because I believe life begins at conception ... it's what separates us from the Islamic jihadists who are out to kill us."
Huckabee also got the biggest laugh of the night, criticizing US lawmakers for overspending. "We've had a Congress that's spent money like John Edwards at a beauty shop," he said lampooning a Democratic presidential candidate over his reported 400 dollar haircut.
McCain had opened the quick-fire showdown warning Democratic bids to force Bush to bring troops home from Iraq risked US security.
"We must succeed and we cannot fail, and I will be the last man standing if necessary," he said.
"If we fail in Iraq, we will see Iraq become a center for Al-Qaeda, chaos, genocide in the region, and they'll follow us home," McCain said.
Romney framed the Iraq war as part of a global struggle against jihadism and also hit out against a troop withdrawal.
"We could have the Iranians take over the Shiite South, and perhaps most frightening, you could have Al-Qaeda play a dominant role among the Sunnis and then have a setting where you'd have something far worse than Afghanistan on (your) hands."
Kansas Senator Sam Brownback, another longshot hope, took aim at US Senate Democratic majority leader Harry Reid, who declared in April that the war in Iraq was "lost."
"We haven't lost," he said.
The debate also included other long-shot candidates: former Virginia Governor Jim Gilmore, conservative Colorado congressman Tom Tancredo, Wisconsin Governor Tommy Thompson and Representative Duncan Hunter.
Several potentially strong candidates yet to declare candidacies were not at the debate, including former senator and television star Fred Thompson.
