FORT LAUDERDALE, Fla. -- Republican Rudy Giuliani Thursday defended a campaign ad that uses images from the Sept. 11, 2001, terrorist attacks, saying other candidates have relied on similar pictures.

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The television ad features images of firefighters at the World Trade Center after the attacks. It draws comparisons between the response to those attacks and the nation's response to being attacked before entering World War II.

"When you challenge Americans, there's no country that stands up stronger and better than the United States of America," Giuliani says in the ad. "When you try and take something away from us like freedom, my goodness, Americans are going to be one in resisting you.

"So, the Islamic terrorists would make a terrible mistake if they confuse our democracy for weakness. Our democracy means we disagree with each other, but when you come and try and take away from us our freedom. When you try and come here and kill our people, we're one and we're going to stand up to you and we're going to prevail," he says.

The Sept. 11 attacks made the former New York mayor a national political figure.

"It's a part of my life that helps define me. It's not the only thing that defines me," Giuliani said, adding that he also has run ads about his record as mayor.

For weeks, Giuliani has portrayed himself as the leader who oversaw the social and economic turnaround of a city. But he had kept his role during the hours and days after the Sept. 11 terrorist attacks out of his ads.

Now, with the New Hampshire primary less than two weeks away, Giuliani draws attention to that tragedy with a national ad meant to get widespread attention.