US President George W. Bush accused Democrat John Kerry in their final debate of not taking terrorism seriously, as the senator countered that "we are not as safe as we ought to be."

US President George W. Bush (R) and Democratic presidential candidate John Kerry shake hands after the final televised debate at Gammage Auditorium, Arizona State University, in Tempe, Arizona. The 90-minute session focus on domestic issues including health care, the economy, taxes, social issues and education. [Reuters]

With millions of Americans watching the 90-minute political prizefight, Bush charged that Kerry was a tax-raising, out-of-the-mainstream leftist while his rival pointed to heavy job losses since the president took office.

The candidates, hoping to break open their deadlocked race just 20 days before the November 2 election, traded blows on the economy, health care, taxes and education, with Iraq and terrorism looming large from the get-go.

"This president, regrettably, rushed us into a war, made decisions about foreign policy, pushed alliances away," said the senator from Massachusetts. "We are not as safe as we ought to be."

"My opponent just this weekend talked about how terrorism could be reduced to a 'nuisance,' comparing it to prostitution, illegal gambling," Bush said, quoting a Kerry interview. "That attitude and that point of view is dangerous."

The Democrat accused Bush of letting Osama bin Laden, the architect of the September 11, 2001 attacks, slip away and pointed to Bush's comments six months later that he was not concerned about bin Laden's fate.

"Gosh, I just don't think I ever said I'm not worried about Osama bin Laden. It's kind of one of those exaggerations," said Bush, who has repeatedly accused Kerry of being fickle and unreliable on national security issues.

Within moments, the Kerry campaign had sent reporters a quotation from a March 13, 2002 press conference in which Bush said of bin Laden: "I truly am not that concerned about him."

The president aggressively attacked Kerry for voting for tax increases or against tax cuts, and concluded: "You know, there's a mainstream in American politics -- and you sit right on the far-left bank."

In response, the senator summoned a reference to the main character of a popular television drama about a mafia family, saying: "Being lectured by the president on fiscal responsibility is a little bit like Tony Soprano talking to me about law and order in this country."

On health care, Bush accused Kerry of having proposed a government takeover of medical treatment. Kerry denied the charge and said that Bush had let millions lose health insurance.

On the divisive issue of gay marriage, Bush said "consenting adults can live the way they want to live" but again endorsed a constitutional amendment forbidding homosexuals to marry.

"The president and I share the belief that marriage is between a man and a woman. I believe that. I believe marriage is between a man and a woman," said Kerry, who restated his opposition to the constitutional amendment.

The president and his challenger both spent Wednesday boning up for the debate. Some 109 million viewers watched the first two sessions and polls suggested the faceoffs could play a key role in swinging undecided voters.

National polls have shown the two candidates running neck and neck, with just a handful of battleground states truly up for grabs in the battle to secure the 270 electoral college votes needed to win the White House.

Kerry's campaign has crowed that he enjoys the momentum after what was widely interpreted as a victory over Bush in their first debate on September 30 and a draw on October 8.

Earlier in the day, the leading US gun-rights group, the National Rifle Association, unsurprisingly endorsed Bush.

The national deficit became a hot issue Wednesday, with The New York Times giving front-page treatment to a study of both candidates' platforms that showed they would aggravate the shortfall by 1.3 trillion dollars over a decade.

The study by the non-partisan but deficit-hawk Concord Coalition portrayed the two men reaching the same result by opposing roads.

Bush would slash taxes by more than US$1.2 trillion and add US$82 billion in spending, the group said. Kerry would cut taxes by US$500 billion and raise spending by 771 billion, mostly on health care.