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."