NEW YORK (Reuters) - Rudy Giuliani rose to national fame in the aftermath of the September 11 attacks, but experts say his moment as “America’s mayor” is both the biggest asset and potential liability in his White House bid.

Republican presidential candidate former New York City Mayor Rudy Giuliani takes the stage during Fox News Channel Republican Presidential debate at the University of New Hampshire in Durham, September 5, 2007. REUTERS/Brian Snyder

On the eve of the sixth anniversary of the World Trade Center attack, experts warned there was a fine line between Giuliani emphasizing his 9/11 leadership as mayor of New York and politicizing the al Qaeda strike that killed 2,750 people in the city.

“This is America’s mayor trying to become America’s president,” Lee Miringoff, director of the Marist Institute for Public Opinion, said of Giuliani, who is leading public opinion polls for the Republican 2008 presidential nomination.

“When he was first running it was largely a plus ... but if he is going to have front-runner status everything is under the microscope,” Miringoff said. “Some people are finding his comments about everything he did as mayor as a bit of a reach.”

Giuliani, known for his brash style and hot temper when he was mayor, is focusing on issues of national security and strong leadership as he woos voters across the country.

Critics say that while Giuliani was a reassuring presence on September 11, he made mistakes preparing the city for an emergency prior to the attacks.

They accuse him of ignoring advice of police and emergency management experts by putting the city’s emergency command center in the World Trade Center complex, which had been bombed in 1993 and was a presumed target.

The command center had to be abandoned on September 11, 2001, after the attack and as a result, police and fire commanders could not coordinate search and rescue efforts. The National Institute of Standards and Technology concluded in a 2005 report that emergency responder lives likely were lost at the trade center because of the lack of communication.

While Giuliani has attended the previous September 11 memorial services, several groups representing some firefighters and families of victims do not want him to speak at Tuesday’s commemoration.

“He’s running for president of the United States on the back of my dead son,” said Jim Riches, a deputy chief of the New York Fire Department whose firefighter son Jimmy, 29, died when the Twin Towers collapsed.

“His legacy from 9/11 should be all the sick and dying firefighters and first responders, construction workers and everybody else, because he was too busy running around giving speeches and making tens of millions of dollars,” he said.

Thousands of rescue workers who combed through the debris of the collapsed World Trade Center have developed health problems from breathing the dust and fumes of the buildings.

Riches, who spent several weeks in a coma in 2005 after suffering respiratory failure that he says was a result of working at Ground Zero, vowed he and other 9/11 families would “get the word out about Rudy Giuliani and how he failed us.”

Last month Giuliani formed a “first responders” support group to defend his record as mayor, but he told a Republican candidate debate last week that he is not “running on what I did on September 11.”

“I’m running on the fact that I was mayor of the largest city in the country, the third-largest government in the country,” he said.

Tony Carbonetti, a Giuliani aide, said in a statement on Monday the former mayor would never politicize 9/11.

Steven Cohen, a public administration professor at Columbia University in New York, said Giuliani was a good mayor, but that he also alienated a lot of people during his eight years at City Hall.

“The few days after 9/11 were really days where he was an exemplary leader. He helped build confidence in the city again and really helped people get back on their feet,” Cohen said. “He was certainly not a consensus builder in this city and is probably exaggerating his claims of being a super mayor.”