OXFORD, United States - John McCain and Barack Obama battled in the shadow of the US finance crisis late Friday in a first presidential debate crackling with sharp disputes over the economy, Iraq and terrorism.
Democrat Obama, 47, vying to make history as America's first black president, branded McCain as an inheritor of President George W. Bush's unpopular legacy of "failed" economic and foreign policies.
Republican McCain, 72, presented himself as a reformer and posed as a superior potential commander-in-chief, repeatedly saying Obama did not "understand" foreign policy threats or was "naive" in his outlook to the world.
"I don't think I need any on-the-job training. I'm ready to go at it right now," McCain, 72, said.
Obama came across as polished and well briefed, and seemed to meet the threshold many analysts set for him going in as a credible future leader of the United States.
Less than 40 days before election day on November 4, differences over the war in Iraq festered throughout the debate on a red carpeted stage at the University of Mississippi.
Obama claimed credit for opposing the invasion in 2003 and McCain said he had been instrumental in pushing the successful surge strategy.
"We are winning in Iraq and we'll come home. And we'll come home as we have when we have won other wars and not in defeat," McCain said, accusing Obama of denying the achievements of US troops in the war.
But Obama hit back, saying "six years ago I stood up and opposed this war," condemning McCain for standing with Bush over 2003 US-led invasion to topple dictator Saddam Hussein.
"I wish I had been wrong for the sake of the country and they had been right but that's not the case," Obama said.
"When the war started you said it was quick and easy, you said we knew where the weapons of mass destruction were. You were wrong.
"You said that we were going to be greeted as liberators. You were wrong. You said that there was no history of violence between Shia and Sunni and you were wrong."
But McCain went on the attack over Obama's offer to offer dialogue to Iran.
"It isn't just naive, it is dangerous," McCain, warning that a nuclear armed Tehran threatened a "second Holocaust."
Ironically, observers believe that it is Israel or the US that is likely to trigger a ‘Holocaust’ against the Iranians, and many critics already accuse Tel Aviv of carrying out a miniature but continuous Holocaust against the Palestinians.
Obama agreed a nuclear Iran would be a "gamechanger" but disagreed with the Republican's opposition to diplomacy with Tehran and other US foes, and stressed Iran had been empowered by the Iraq war.
Obama reiterated his vow to launch military attacks on extremists in Pakistan if Islamabad was unwilling or able to act, prompting a rebuke from McCain: "You don't say that out loud."
Obama also recalled an unguarded moment by McCain months ago on the campaign trail in Iowa.
"Coming from you, who, you know, in the past has threatened extinction for North Korea and sung songs about bombing Iran, I don't know how credible that is."
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