"Those of us who've spent time with him and have had a part of forming his spiritual life can testify with certainty of his commitment to Christ," said Pastor Joel Hunter of Northland, A Church Distributed, in Longwood, Fla., according to McClatchy Newspapers.
The Florida megachurch pastor said he regularly sends devotionals to Obama and prays with him over the phone.
The Pew Forum on Religion and Public Life released new poll results Thursday revealing that 18 percent of Americans say Obama is a Muslim, up from 11 percent in March 2009. Meanwhile, the percentage of those who believe the U.S. president is a Christian decreased from 48 percent to 34 percent. Forty-three percent say they do not know his religion.
Among those who say Obama is a Muslim, 11 percent say they learned about the president's religion through his own words and behavior, and 60 percent cite the media.
Hunter, who served on Obama's 25-member faith advisory council this past year and who describes himself as a conservative evangelical, told McClatchy that there are a lot of Americans who are misinformed and "just buy into the strongest voice."
Evangelist Franklin Graham believes Obama's background has raised doubts among Americans.
"I think the president's problem is that he was born a Muslim, his father was a Muslim," Graham told CNN.
But Graham said "it's obvious that the president has renounced Islam" and accepted Jesus Christ.
"That is what he says he has done, I cannot say that he hasn't. So I just have to believe that the president is what he has said."
The White House also addressed the confusion over Obama's faith on Thursday, stressing that Obama is "a committed Christian."
"The president's Christian faith is a part of who he is, but not a part of what the public or the media is focused on every day," Jen Psaki, deputy communications director for the White House, told CNN.
More than a year into his presidency, Obama has chosen not to join any specific church community. He has said that he does not want to be disruptive to the city or to churchgoers. He and his family have visited a few local churches during such occasions as Easter and have at times attended Evergreen Chapel at Camp David, the president's country residence in Frederick County, Md.
Given the latest poll findings, Hunter believes it may be time for the White House to be more public about what the president does to be an active Christian.
Notably, the Pew survey found that more than half (53 percent) of Americans say Obama mentions his religious faith and prayer "the right amount" while 19 percent say he mentions his faith "too little."
The survey was conducted July 21-Aug. 5 among 3,003 respondents.