Former presidential candidate John Edwards, who won praise and sympathy as he campaigned side-by-side with his cancer-stricken wife, Elizabeth, admitted Friday he had had an extramarital affair with a woman who produced videos for his campaign.

Edwards said he made a serious error in judgment when he had an affair and is ashamed of his conduct.

In a statement, the former Democratic presidential candidate also said he informed his wife about his affair with 42-year-old Rielle Hunter in 2006 and has asked her forgiveness. Edwards said he is not the father of the woman's daughter and is willing to take a test to determine the 5-month-old baby's paternity.

He said the affair lasted for a short time in 2006.

Until Friday, Edwards had denied reports in the National Enquirer that he had an affair while his wife, Elizabeth, was battling cancer. He first admitted to the affair in an interview with ABC News.

Edwards spoke about his affair with Rielle Hunter, 42, for an interview to be broadcast Friday night on the ABC News show "Nightline."

A former campaign aide, Andrew Young, has said he was the father of the child, ABC News said.

Edwards was previously linked to the woman by The National Enquirer. It recently reported that Edwards, 54, of North Carolina, met with Hunter at the Beverly Hilton in California on Monday night, July 21.

Edwards' political action committee paid $100,000 in 2006 to Hunter's company, Midline Groove Productions. She directed Web videos featuring Edwards.

Edwards was a top contender for the Democratic nomination for president. He placed second in the Iowa caucuses last January but dropped out of the race a few weeks later.

Edwards, a former senator from North Carolina, was the Democratic nominee for vice president in 2004.

The two live in Chapel Hill, N.C., with their children, Emma Claire Edwards, 9, and Jack Edwards, 7. Their eldest daughter, Cate, is a student at Harvard Law School.

Elizabeth Edwards Proud Of Husband's Courage

In a statement given to The Associated Press, Elizabeth Edwards said she and John decided to go public now because of tabloid stories suggesting that John was spending time with Hunter's child born earlier this year. The Edwardses say the child was not fathered by John.

Elizabeth Edwards said it wasn't easy finding out about the affair, but she said the healing process was "oddly made somewhat easier" after she was diagnosed with breast cancer a year ago in March.

She said she's "proud" of what she calls the "courage" her husband has shown by his honesty in the face of shame.

Hunter Says She Took Trip To Africa With Edwards

Hunter told the television show "Extra" last year that she and John Edwards took a trip together to Africa.

She called it an amazing and "life-altering" experience.

In the interview recorded before the affair became public, Hunter said she had approached Edwards in New York with an idea for producing Internet videos for his campaign. She said she considers herself "courageous" and felt she could help in some way.

Hunter described Edwards as open and ready to try new things. She said she found him very real, authentic and inspirational.