COLLEGE STATION, Texas — Seeking to defuse suspicions about his Mormon faith, Mitt Romney declared here Thursday in a heavily anticipated address that the nation's foundation of religious liberty bars a religious test for higher office, but unites the country under a common moral heritage that he would champion if elected president.

Romney did not dwell on the doctrines of his faith, mentioning the word Mormon only once. But he promised that he would not be beholden to the authorities of his church, and he devoted most of his 20-minute address here at the George H.W. Bush Presidential Library to a call for a robust role for religion in public life.

"I will take care to separate the affairs of government from any religion, but I will not separate us from the God who gave us liberty," he said, drawing applause from an audience of about 300 invited guests, including supporters and religious leaders. "Nor would I separate us from our religious heritage."

The theme appeared calculated to resonate with conservative evangelical Christians. While many in that group consider Mormonism to be heretical, they also believe that the country was founded as a "Christian nation" and have expressed mounting alarm over efforts to enforce the separation of church and state by removing expressions of faith from the public square.

Romney said as recently as a few weeks ago that his political advisers did not want him to give such a speech, fearing that it would draw too much attention to his religious beliefs. But it has since become clear that Romney is facing a vigorous challenge in Iowa's first-in-the-nation Republican caucuses from Mike Huckabee, a former Baptist pastor whose rise in the polls has been fueled by evangelical Christians.

His speech was peppered with declarations, sure to appeal to conservatives, about the importance of religion as a motivating force for good in the nation's history, whether it be in the civil right's movement, or the anti-abortion cause, although he failed to mention he had supported abortion-rights until relatively recently.

"No movement of conscience can succeed in America that cannot speak to the convictions of religious people," he said.

He went to say: "In recent years, the notion of the separation of church and state has been taken by some well beyond its original meaning. They seek to remove from the public domain any acknowledgment of God. Religion is seen as merely a private affair with no place in public life. It is as if they are intent on establishing a new religion in America — the religion of secularism. They are wrong."

When he did talk about the Mormon religion, Romney said he would not distance himself from it, saying he believed in it and strived to live by its precepts.

"Some believe such a confession of my faith will sink my candidacy," he said. "If they are right, so be it. But I think they underestimate the American people. Americans do not respect believers of convenience. Americans tire of those who would jettison their beliefs, even to gain the world."

Romney said it was inappropriate for a presidential candidate to be asked to explain the details of his or her faith.

"There are some who would have a presidential candidate describe and explain his church's distinctive doctrines," he said. "To do so would enable the very religious test the founders prohibited in the Constitution. No candidate should become the spokesman for his faith. For if he becomes president he will need the prayers of the people of all faiths."

His one allusion to the fact that many people, especially evangelical Christians, do not consider Mormonism to be part of Christian orthodoxy came when Romney spoke of his belief in Jesus Christ. In a notable departure from the way he has talked about the subject on the stump, he added a caveat that other people might have different interpretations, an apparent reaction to the way some evangelicals have recoiled from Romney's past mentions of Jesus Christ, apparently intended to signal some kinship with them.

"I believe that Jesus Christ is the Son of God and the Savior of mankind," Romney said. "My church's beliefs about Christ may not all be the same as those of other faiths. Each religion has its own unique doctrines and history. These are not bases for criticism but rather a test of our tolerance. Religious tolerance would be a shallow principle indeed if it were reserved only for faiths with which we agree."

The speech drew inevitable comparisons to John F. Kennedy's speech nearly a half-century ago in Houston, when he strolled directly into the lion's den of Protestant religious opposition to his Roman Catholicism, and promised that he would uphold the separation of church and state before a gathering of Southern Baptist ministers. Romney alluded to that event himself.

Romney's address on Thursday, however, differed significantly from that signal moment in recent history, which historians say was a turning point in the 1960 election. For one thing, Kennedy later took questions hurled at him from the ministers, many of them hostile, while Romney spoke before a friendly audience whose front row included four of his five sons and his wife, Ann, as well as many people affiliated with the campaign.

Like Kennedy, Romney pointed to his public record — his governorship of Massachusetts — as proof of his independence from his church's hierarchy. He said he would abide by what Abraham Lincoln called America's "political religion," promising to "defend the rule of law and the Constitution."

"When I place my hand on the Bible and take the oath of office, that oath becomes my highest promise to God," he said. "If I am fortunate to become your president, I will serve no religion, no one group, no one cause, and no one interest. A president must serve only the common cause of the people of the United States."

Romney took his audience on something of a journey through the country's religious heritage that included mentions of everyone from Anne Hutchinson, the religious dissident banned from the Massachusetts Bay Colony in the 1600s, to Brigham Young, who led persecuted Mormons to Utah in the 19th century.

"We do not insist on a single strain of religion," he said. "Rather, we welcome our nation's symphony of faith."

He closed with a stirring portrait of a moment in the early days of the First Continental Congress in Philadelphia during the fall of 1774. Boston was occupied by British troops, he said, and there was pervasive fear of war.

Someone suggested that the members of the congress pray, Romney said, but there were objections raised that there were too many divisions among the delegates, who included Episcopalians, Quakers, Anabaptists, Catholics and others.

"Then Sam Adams rose, and said he would hear a prayer from anyone of piety and good character, as long as they were a patriot," Romney said. "And so together they prayed, and, together, they fought, and together, by the grace of God, they founded this great nation."

That statement drew Romney a standing ovation.