By Beth Fouhy

NEW YORK | Mayor Michael R. Bloomberg is not known for public displays of emotion. So he startled more than a few observers this week in a speech supporting a proposed mosque near ground zero, recalling the firefighters who died in the Sept. 11, 2001, attacks.

“In rushing into those burning buildings, not one of them asked: ‘What God do you pray to? What beliefs do you hold?'” Mr. Bloomberg said, his voice breaking. “We do not honor their lives by denying the very constitutional rights they died protecting.”

The debate over the mosque has emerged as a national proxy battle over religious freedom and the symbolic significance of the World Trade Center site. And no public figure has been more identified with the mosque than Mr. Bloomberg, who has been willing to yoke his own stature and reputation to a project its critics call a victory for terrorists.

“He believes in diversity and the greatness of New York is in the diversity of its people,” said Hank Sheinkopf, a Democratic strategist who has worked for Mr. Bloomberg. “He’s consistent. He doesn’t owe anything to anyone, and my hunch is that he’s not out of line with where most people in the city are on this issue.”

The billionaire mayor, a Republican-turned-independent, has never shied from championing a cause — from knocking proposed tax increases on hedge-fund managers to banning trans fats in the city’s restaurants. But he has been unusually forceful on the mosque issue, even as otherwise loquacious New York politicians such as Democratic Sen. Charles E. Schumer have largely steered clear.

After spending weeks answering questions about the mosque, Mr. Bloomberg decided to give a speech outlining his views on the matter. “He wanted to speak proactively, forcefully and at some length,” said Deputy Mayor Howard Wolfson, who helped craft the address.

Mr. Bloomberg delivered it Aug. 3 surrounded by a multicultural array of religious leaders, with the Statue of Liberty as a backdrop.

“I believe that this is as important a test of the separation of church and state as we may see in our lifetime, and it is critically important that we get it right,” he said.

The mosque, to be located two blocks from ground zero, would be part of a 13-story, $100 million Islamic center that would also feature a 500-seat auditorium, swimming pool and gym. It’s a project of the Cordoba Initiative, an advocacy group that promotes improved relations between Islam and the West.

The mosque has drawn vocal opposition from many relatives of the 9/11 victims and local and national Republican leaders, including former Alaska Gov. Sarah Palin and former House Speaker Newt Gingrich. The Anti-Defamation League, a Jewish civil rights group, announced its opposition as well.

Some critics object to any mosque being built so close to the site where nearly 3,000 people died at the hands of Muslim extremists. Others say they have specific concerns about Cordoba and its director, Imam Feisal Abdul Rauf, who said in an interview shortly after 9/11 that U.S. policies were partly responsible for the attacks. Mr. Rauf also refuses to disclose who is funding the mosque’s construction.

Mr. Bloomberg has steadfastly rejected those concerns.

He views the mosque, in part, as a redevelopment project like any other — carrying with it the possibility of creating jobs and bringing something new and interesting to a stretch of Lower Manhattan.

Mr. Bloomberg is staunchly pro-development; during his 8½ years in office, his administration has rezoned thousands of blocks in dozens of neighborhoods, welcoming new construction in every corner of the city.

The mayor has roundly dismissed complaints about the mosque from GOP officials while making what many might view as a fundamentally conservative argument: that government should not interfere in private enterprise.

“This building is private property and the owners have a right to use the building as a house of worship,” Mr. Bloomberg said. “The government has no right whatsoever to deny that right.”

The mayor scoffed when asked whether he had any concerns about Mr. Rauf. “My job is not to vet clergy in this city,” he said.

But Debra Burlingame, a spokeswoman for some 9/11 victims’ families, said Mr. Bloomberg is being played, because Mr. Rauf has links to Muslim extremist groups and advocates the eventual “Islamization” of the U.S.

“The mayor is demagoguing an issue that is wreaking agony on family members of those killed in the name of Allah,” Miss Burlingame said. “Bloomberg says it’s about the separation of church and state? The imam doesn’t believe in the separation of church and state. He’s laughing up his sleeve.”

Mr. Rauf did not reply to a phone message. But his wife, Daisy Khan, has said the Islamic center would include a memorial to the 9/11 victims.

“When you’re running for office, you tend not to take controversial positions,” Mr. Sheinkopf said. “Bloomberg is not running.”