A former aide to John Edwards claims the former U.S. senator asked him to say he fathered a child with Edwards' mistress, a publishing industry source said.

The aide, Andrew Young, has sold a proposal to St. Martin's Press for a book in which he would say Edwards told him he "would be taken care of for life" if he would say he was the father of a baby born to Rielle Hunter. Edwards -- who represented North Carolina for one term in the U.S. Senate and was the Democratic Party vice presidential nominee in 2004 -- has admitted an affair with Hunter but has denied he is the baby's father.

In the proposal, Young quotes Edwards as begging him to claim he is the father of Hunter's child, The New York Times reported.

"'You know how much I love you,' Edwards said. 'You know I'd walk off a cliff for you, and I know you'd walk off a cliff for me,'" Young wrote in the pitch for his book. "'I will never forget this. And I will always be there for you.'"

The newspaper cited a book publishing executive as the source for its information about the proposal, which Young sold to St. Martin's last week. The price has not been reported.

Young wrote in the proposal that he had been questioned by the FBI and subpoenaed to appear before a federal grand jury. Prosecutors are looking into whether Edwards' campaign funds were used in any possible effort to keep the affair with Hunter from being exposed.