Democratic presidential nominee Barack Obama said Sunday that his answer to the question "When does a baby get human rights?" at the recent Saddleback Church civic forum was probably too flip.

Less than a month ago, Obama had answered moderator Pastor Rick Warren at the nationally televised event that it was "above my pay grade" to determine when life begins.

But on Sunday, during an interview with ABC News, Obama acknowledged the response was "probably" too flip.

"Yes. I mean, what I intended to say is that, as a Christian, I have a lot of humility about understanding when does the soul enter into...," he explained.

"It's a pretty tough question," he continued. "And so, all I meant to communicate was that I don't presume to be able to answer these kinds of theological questions."

Rick Warren, in an interview after the forum, said he thought Obama needed to be more specific with his answer.

"[T]o me, I would not want to die and get before God one day and go, 'Oh, sorry, I didn't take the time to figure out' because if I was wrong, then it had severe implications for my leadership if I had the ability to do something about it," Warren had said in a Beliefnet.com interview.

"But to just say 'I don't know' on the most divisive issue in America is not a clear enough answer for me," he added.

Obama, in his interview Sunday, had also explained that abortion is a moral issue and he does not think the government "criminalising" the decision of families is the best way to reduce the practice.

Meanwhile, Obama's running mate, Senator Joe Biden of Delaware, said during a separate interview on NBC's "Meet the Press" Sunday that as a Roman Catholic he accepts the Church's teachings that life begins at conception.

However, he thinks it is inappropriate in a pluralistic society to impose his judgment on others.

National surveys show that Obama has been significantly less popular among highly religious white voters. A Gallup Poll survey, released on Friday, show that 65 per cent of non-Hispanic white registered voters who attend church weekly support Republican candidate John McCain, compared to 26 per cent who support Obama.

Overall, McCain is slightly leading Obama among registered voters, according to the latest Gallup Poll Daily tracking update. McCain has the vote of 48 per cent of registered voters, while Obama has 45 per cent. The results are based on interviews with 2,765 registered voters on September 4 to 6.