"We do not claim to know all the ways of Providence," he said in his State of the Union address last month. "Yet we can trust in them, placing our confidence in the loving God behind all of life, and all of history. May he guide us now."
The day the space shuttle Columbia ripped apart in the sky, killing seven astronauts, Bush, quoting the prophet Isaiah, said of the victims: "Because of his great power and mighty strength, not one of them is missing."
The sincerity of the president's religious commitment seems beyond doubt. Bush is a churchgoing Methodist who said he has not drunk alcohol since 1986, when he recommitted himself to Jesus Christ. In 1999, when asked in a campaign debate what political philosopher he most identified with, Bush named Christ, "because he changed my heart."
At the same time, Bush's stepped-up efforts to express his faith coincide with a White House drive to court religious conservatives in advance of the president's 2004 re-election campaign.
The president's top political adviser, Karl Rove, has concluded up to 4 million Christian conservatives who probably would have voted for Bush instead stayed home in the 2000 election. Rove said a year ago that "we have to spend a lot of time and energy" drawing them back into politics.
Even 1 million extra votes could supply an enormous boost next year for Bush, who won the presidency by the tightest of margins.
Bush's increasing use of religious language has drawn criticism from those who advocate a strict separation of church and state. They say his message is growing more exclusionary for Americans who do not share his beliefs.
Some foreign-policy analysts say Bush also is taking a sizable risk in solidifying his image as a Christian believer when he is on the verge of launching a war against Iraq. Since the U.S. war on terrorism began, radical Islamic leaders and terrorist groups have vilified the anti-terror drive as a holy war against people of Islamic faith.
In speaking of terrorism and of the U.S. confrontation with Iraq, Bush typically goes out of his way to clarify that the enemies are terrorists and outlaw regimes, not Muslims.
Terrorists, he said, have taken hostage what Bush has described as a peaceful Islamic religion.
Yet some analysts say the president undercuts those efforts if, even in events unrelated to war, he uses language suggesting to the world that the U.S. leader is a devout Christian.
"If the war is put too much in the context of, 'The Christian faith is somehow burdened, so we have to assume the role of good Christians,' it sends a very negative signal," said Edward Walker Jr., president of the Middle East Institute and a State Department specialist during the Clinton years and the start of the Bush administration.
"The president has been very careful that no one misinterprets this as a fight between religions, but he has to be careful about quoting evangelical hymns," Walker said. "That kind of thing gets picked up immediately. There are people actually looking for it."
Karen Hughes, a former top adviser to Bush who still helps draft major speeches, said that by meeting frequently with Muslim leaders, visiting a mosque and praising Islam, the president "has gone to great lengths to make it clear" the war is not about religion.
"At moments of tragedy or great challenge, presidents have frequently called on faith for comfort and strength," Hughes noted.
The president is careful to recognize, she said, that "America is a nation of many faiths." But she added: "We were founded on the belief that we were given certain rights by a creator."
Bush was reared an Episcopalian but converted to Methodism after he married. Although he has not described himself as "born again," he underwent what he called a transforming experience in 1986, when he engaged in a long, probing conversation with the Rev. Billy Graham. Bush soon became a teetotaler and renewed his faith in Christ.
Since taking office, he has cultivated an atmosphere at the White House that is flecked with religious feeling. He often begins Cabinet meetings with a prayer.
David Frum, a speechwriter for Bush until last year, wrote in his recent book, "The Right Man: The Surprise Presidency of George W. Bush," about first entering the White House. Frum said he heard a staff member say to Bush's chief speechwriter, Michael Gerson, "Missed you at Bible study."
"The news that this was a White House where attendance at Bible study was, if not compulsory, not quite uncompulsory, either, was disconcerting to a non-Christian like me," Frum wrote.
From Bush's first days in office, his speeches — often drafted by Gerson, an evangelical Christian — frequently have included religious references, usually subtle.
The president committed a widely noted error soon after the Sept. 11, 2001, attacks, when he spoke of leading a "crusade" against terrorism. Muslim leaders reacted with anger and bewilderment, saying people of Islamic faith could interpret the war as being directed at them.
Ari Fleischer, Bush's spokesman, said at the time that "the president would regret if anything like that was conveyed." Bush never used the term publicly again.
But some analysts say the president, with war in Iraq looming, would be wise to avoid overt reminders that he is a devout Christian. Educated Muslims who follow news in the United States, the analysts say, know that the Rev. Franklin Graham — who spoke at Bush's inauguration and is Billy Graham's son — called Islam "a very evil and wicked religion" after the Sept. 11 attacks on the World Trade Center and the Pentagon.
"It wasn't Methodists flying into those buildings, and it wasn't Lutherans," Graham said later. "It was an attack on this country by people of the Islamic faith."
John Voll, associate director at Georgetown University's Center for Muslim-Christian Understanding, suggests Bush should feel free to invoke faith in general but might avoid specific references to Christianity.
"To the extent that an American statesman can put himself forward as a real believer, in many ways that's a positive dimension even in a hostile environment," Voll said. "He becomes essentially something understandable, a man of faith.
"But evangelical Christianity is identified with Islamaphobia," Voll said. "It is essential that Bush make clear that he is not in any way associated with them."