March 30, 2011 -- President Obama says he's been doing "a lot of praying" in recent weeks while faced with tough choices on Libya and other crises at home and abroad.

"I am praying that I'm making the best possible decisions, and that I've got the strength to serve the American people well," he said in an interview Tuesday with ABC News' Diane Sawyer.

While the president has not shied away from openly discussing his prayer life, Obama's comments are the latest reminder that he believes faith in God has helped him navigate the presidency's difficult moments.

At the National Prayer Breakfast in Washington last month, Obama described how the shooting tragedy in Tucson, Ariz., had deepened his faith and how watching his daughters grow up makes him lean on God a little bit more.

"My prayers sometimes are general: Lord, give me the strength to meet the challenges of my office," he said. "Sometimes they're specific: Lord, give me patience as I watch Malia go to her first dance. Where there will be boys, Lord, have that skirt get longer as she travels to that dance."

Despite Obama's public professions on religion and spirituality, many Americans continue to doubt the president's faith.

Nearly one in five Americans incorrectly believes that Obama is a Muslim, according to a poll by the nonpartisan Pew Forum on Religion and Public Life released late last year.

The poll found the number surveyed who knew correctly that Obama is Christian actually declined, from 48 percent in March 2009 to 34 percent in August 2010. Forty-three percent of Americans now say they don't know what Obama's religion is at all.

The president has defended against the skepticism, and said that his faith has helped him endure the difficult questions.

"My Christian faith ... has been a sustaining force for me over these last few years -- all the more so when Michelle and I hear our faith questioned from time to time," Obama said last month. "We are reminded that ultimately what matters is not what other people say about us but whether we're being true to our conscience and true to our God."

Obamas Not Church Members in D.C.

The Obamas, once regular churchgoers, have not formally joined a new church since moving to Washington, D.C., and have publicly attended services less than a dozen times.

But sources familiar with the president's personal life in the White House say Obama remains a faithful Christian, practicing his beliefs regularly in private with family and the aid of his BlackBerry.

"Barack Obama is a Christian. He's always been clear and unapologetic about that, and he's comfortable with his own faith," said Rev. Jim Wallis, an Obama friend and spiritual adviser. "But I think the president, particularly a president, needs the kind of pastoral care or spiritual counsel with people who don't have a political agenda. And it's hard for a president to get that."

Obama told Terry Moran of ABC "Nightline" that his personal BlackBerry, which he famously fought with the Secret Service to keep, has actually become a tool for keeping the faith during his time in office.

"My Faith and Neighborhood Initiatives director, Joshua DuBois, he has a devotional that he sends to me on my BlackBerry every day," Obama said in an interview during his first year as president. "That's how I start my morning. You know, he's got a passage, scripture, in some cases quotes from other faiths to reflect on."

The president is also said to be fond of worship services at the chapel at Camp David.

Most Presidents Not Church Members

Historians say a president's not formally joining a Washington, D.C., church is consistent with precedent.

George W. Bush and his father, George H.W. Bush, were both "frequent attendees" at local churches but did not formally join a D.C. congregation.

Ronald Reagan publicly articulated the values of evangelical Christianity, but rarely attended church services. He also never became a formal member at a congregation in Washington.

Jimmy Carter, who joined First Baptist Church in Washington, stands out as one of the most prominent presidential church-goers. He attended 72 Sunday services at First Baptist while in office, according to records kept by the Carter Library.

And Bill and Hillary Clinton, who attended Foundry United Methodist church near the White House regularly but did not formally join, are perhaps the exception in modern history for first family participation in church life, experts say.

Obama and all former U.S. presidents professed faith in Christianity, with most men identifying as Episcopalians, according to the Pew Forum on Religion and Public Life. Obama is the first U.S. president who affiliates with the Christian Protestant denomination, the United Church of Christ.

ABC News' Sunlen Miller contributed to this report.