June 11, 2009  -- Chastity Bono, daughter of Cher and the late Sonny Bono, is undergoing gender reassignment surgery, his publicist confirmed to ABCNews.com.

"Yes, it's true -- Chaz, after many years of consideration, has made the courageous decision to honor his true identity," Howard Bragman said. "He is proud of his decision and grateful for the support and respect that has already been shown by his loved ones. It is Chaz's hope that his choice to transition will open the hearts and minds of the public regarding this issue, just as his 'coming out' did nearly 20 years ago.

"We ask that the media respect Chaz's privacy during this long process as he will not be doing any interviews at this time," Bragman added.

Bono, an LGBT civil rights advocate, journalist, author and musician, began the process of changing his gender earlier this year, following his 40th birthday. The Gay & Lesbian Alliance Against Defamation (GLAAD) has already voiced its support of him.

"Chaz Bono's decision to live his life authentically represents an important step forward, both for him personally and for all who are committed to advancing discussions about fairness and equality for transgender people," GLAAD president Neil G. Giuliano said in a statement to reporters. "Coming out as transgender is an extremely personal decision and one that is never made lightly."

Bono revealed to his parents that he was a lesbian at age 18 and wrote about the experience in his 1998 memoir, "Family Outing."

In 2002, Bono wrote "The End of Innocence," a second memoir about coming out, his music career, and his partner's death from non-Hodgkin's lymphoma.

Cher Shocked by Chastity's Sexuality

According to Bono's books, Cher was shocked by the news of his sexuality and even banished Bono from her NYC apartment immediately after he came out.

"I'd always had this idea that she would get married and have a family," Cher told People magazine in 1998.

The two since have mended their relationship, though Cher reportedly expressed concern about Bono's weight. Bono participated in VH1's "Celebrity Fit Club 3" in 2003 in an effort to shed pounds.

ABCNews.com's calls and e-mails to Cher's representatives for comment were not immediately returned Thursday.