Christian evangelist Franklin Graham, son of prominent preacher Billy Graham, has stirred up the politically sensitive issue of President Barack Obama's Christian faith, saying he accepted the president at his word that he was a Christian but he could not know what Obama actually believed.

Graham, who has led the Billy Graham Evangelistic Association since his father's retirement, also repeated earlier remarks linking Obama to Islam through his African ancestry and said the Muslim world saw him as a Muslim.

"That's just the way it works. That's how they see him. Of course, he says he didn't grow up that. He didn't believe in that. He believes in Jesus Christ. So I accept that," he said on MSNBC's "Morning Joe" program.

At another point in the interview, he said: "I have no idea what he really believes."

Earlier this month, Obama emphasized his Christian faith at a National Prayer Breakfast, saying he prayed every morning and has crafted key elements of his economic policies in line with Biblical teachings.

White House spokesman Jay Carney, asked about Graham's comments on Tuesday, said the president was more focused on policy issues than on commentary about his personal faith.

Graham said Obama's grandfather and father were Muslims. Obama himself has said although many people in his father's Kenyan village were Muslim, his father did not practice Islam and "wasn't very religious."

The issue of Obama's religious faith has already been raised in the campaign for the November presidential election, as potential Republican opponents assail his record and question his fitness to be re-elected for a second term.

One Republican hopeful, former Pennsylvania senator Rick Santorum, last week told supporters Obama's agenda was "about some phony ideal. Some phony theology. Oh, not a theology based on the Bible. A different theology." When asked about the statement later, Santorum said, "If the president says he's a Christian, he's a Christian."

Questions about Obama's religion by political opponents have sometimes been intertwined with discredited claims that he was born outside the United States and thus ineligible for the office. Graham has aligned himself with that movement in the past.

Graham said in Tuesday's interview: "I've told people this many times, I accept him at what he says. If he says he's a Christian, I accept that. I'm not going to say that he's not."

He raised no doubts about the religious commitment of Santorum and another Republican contender, former House of Representatives Speaker Newt Gingrich. Both men are Catholics.

Speaking about another Republican candidate, Mitt Romney, who is a Mormon, Graham said he would make "a good president" and said "he has the ability" to lead the country. When asked about Romney's Mormon faith, Graham said, "Most Christians would not recognize Mormonism as part of the Christian faith."

Billy Graham was among the most influential U.S. religious leaders of the 20th century, having prayed with every president since Harry Truman. Obama visited Billy Graham at his North Carolina home in 2010.