NEW YORK -- Mayor Michael 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?' " 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 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 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, never has 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 U.S. Sen. Chuck Schumer largely have steered clear.

After spending weeks answering questions about the mosque, 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.

Bloomberg delivered it Tuesday 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 also would 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. Last week, 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. Rauf also refuses to disclose who is funding the mosque's construction.

Bloomberg steadfastly rejected those concerns.

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," Bloomberg said. "The government has no right whatsoever to deny that right."

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