Obama: 'I'm a Christian by choice'

President Barack Obama was forced to open up about his Christian faith on Tuesday when an woman asked him why he was a Christian.

"I'm a Christian by choice," he responded.

It was a "hot topic question", the woman said during an informal conversation on the economy. Obama was meeting with families in the front garden of the home of Andy and Etta Cavalier in Albuquerque, New Mexico, when the question was posed.

Providing a brief account of how he grew up, Obama said his family members "weren't folks who went to church every week".

"My mother was one of the most spiritual people I knew, but she didn't raise me in the church," he said.

Obama became a Christian later in life.

What drew him to Christianity were "the precepts of Jesus Christ" which spoke to him in terms of the kind of life he wanted to lead, he explained.

These precepts included "being my brothers' and sisters' keeper; treating others as they would treat me".

He continued, "I think also understanding that ... Jesus Christ dying for my sins spoke to the humility that we all have to have as human beings – that we're sinful and we're flawed and we make mistakes; we achieve salvation through the grace of God."

In terms of how he's living out his Christian faith, he said he strives and prays to "see God in other people" and "help them find their own grace".

"I think my public service is part of that effort to express my Christian faith," he said.

Only about a third of Americans believe the president is a Christian, a Pew Forum on Religion and Public Life revealed last month. Last year, nearly half held that perception. Meanwhile, some 18 per cent say Obama is a Muslim and the rest do not know his religion.

Following the release of the poll, the White House and several pastors who advise Obama defended the president's faith and assured the public that he is committed to Christ. Florida pastor Joel C Hunter recommended that the White House be more public about what Obama does to be an active Christian.

A few weeks later, Obama and his family made a rare appearance at church for Sunday worship. They attended St John's Church near the White House.

After responding to the question about his faith on Tuesday, Obama added that as the president of the United States, he also believes that "part of the bedrock strength of this country is that it embraces people of many faiths and of no faith".

"Their own path to grace is one that we have to revere and respect as much as our own and that's part of what makes this country what it is," he highlighted.

"We were founded on freedom ... the freedom of religion. That's how this country got started. That's why people came here. We have to constantly, I think, reaffirm that tradition even when it sometimes makes us uncomfortable."

Briefly addressing another "hot topic question" asked by the same woman, Obama reiterated his stance on abortion.

Abortion should be "safe, legal and rare", he said.

The decision should be made by the families and the women involved and not the government, he said.

Regarding late-term abortions, he noted that there are "a whole host of laws on the books" in which the interests shift after a certain period so that there are some restrictions, and "appropriately so".