Raleigh, N.C. — Sources have told WRAL News that they expect former U.S. Sen. John Edwards to admit that he is the father of his former mistress' 18-month-old daughter.

Edwards, a two-time Democratic presidential candidate, confessed last August to having an affair with Rielle Hunter, who served as a videographer on Edwards' 2008 campaign. He has denied fathering her daughter, saying his relationship with Hunter ended before the child was conceived.

The name of the girl's father isn't disclosed on her birth certificate.

Andrew Young, a long-time Edwards aide, initially claimed to be the father of Hunter's child, but he is reportedly writing a book in which he will claim Edwards is the father.

A federal grand jury is investigating whether Edwards' campaign funds were illegally paid to Hunter to keep quiet about the affair.

Hunter spent nine hours last Thursday at the federal courthouse in Raleigh, where the grand jury was meeting. She brought her daughter, Frances, with her.

Young was at the federal courthouse in July when the grand jury was meeting.

Sources said Edwards' public admission could come before the end of the criminal investigation.

"No statement is planned at the moment," Edwards' attorney, Wade Smith, said Friday.