Some evangelical leaders came away from the speech impressed.
The Rev. Rob Schenk, president of the National Ministry Center in Washington D.C., who is neutral in the presidential race, called it "one of the best political speeches on this subject that will likely ever be made."
"As an evangelical, I think he went a long way toward relieving some of the anxieties that evangelicals have experienced about a Mormon president, and I think that's a good thing," said Schenk, who attended the speech along with a number of other religious leaders.
Romney avoided specifics about Mormonism, saying to do so would amount to a "religious test" not in keeping with the strictures of the U.S. Constitution.
The Church of Jesus Christ of Latter-day Saints has an estimated 6 million members in the United States and is based on the belief that the religion's founder, Joseph Smith, found golden tablets in 1827 in upstate New York left behind by ancient Israelites.
Matthew Wilson, political scientist at Southern Methodist University in Dallas, called it a "very powerful speech." But he doubted it "will change anyone's theological scepticism about the Mormon church."
"I certainly didn't hear anything that he said that should disturb evangelicals," said Welton Gaddy, president of the Interfaith Alliance. He said Romney should also have stressed he would protect the rights of those who do not have a religion or who oppose a religion.
Romney said he would not turn his back on his faith, as he said some would prefer.
"I believe in my Mormon faith and I endeavour to live by it," he said. "Some believe that such a confession of my faith will sink my candidacy. If they are right, so be it."
A recent survey by the Pew Research Center found a majority of Americans view the Mormon faith as a Christian religion, but one in four respondents said they would be less likely to vote for a Mormon president.
Romney's campaign is heavily dependent on a victory in Iowa, which on January 3 holds the first of the state-by-state contests to determine which Republican and Democrat will face off in the November 2008 election.
Romney spent millions to build a big lead in Iowa, but the advantage has evaporated in recent weeks, with Huckabee winning support from Christian evangelicals to catch him in the polls.
