U.S. Olympic champion turned reality TV star Bruce Jenner won praise Saturday from celebrities and activists for revealing he is transitioning from male to female, ending long-running speculation he identifies as a woman.

In a highly anticipated, two-hour television interview aired Friday -- hailed by transgender rights' campaigners and his own Kardashian-linked family -- the 65-year-old said he had wrestled with his sexual identity since he was a kid.

"I've always been confused about my gender identity since I was this big," he told ABC's celebrity interviewer Diane Sawyer.

"Here I am, stuck -- and I hate the word -- (a) girl stuck in a guy's body... As of now I have all the male parts and all that kind of stuff."

But asked point blank if he was a woman, Jenner said: "Yes. For all intents and purposes, I'm a woman."

Speculation that the actor, race-car enthusiast and 1976 Montreal Summer Olympics decathlon gold medalist was undergoing a sex change has been rich fodder for supermarket tabloids for months.

Supposed telltale signs, based on paparazzi photos from the streets of Los Angeles, include shaved limbs, long hair worn in a ponytail and what appears to be a sports bra under a T-shirt.

'I am not gay'

Jenner said he identifies himself as "her," but not by a specific name. The ABC interviewer used "he" and "him" throughout, without causing any apparent discomfort for the former Olympian.

He stressed the difference between gender identity and sexuality.

"I am not gay," Jenner said. "I am, as far as I know, heterosexual. I've always been with a woman, raising kids."

Just before making the long-expected announcement, Jenner symbolically let his hair down.

"Let's take the damn ponytail out," he told Sawyer, smiling.

Lesbian, gay, bisexual and transgender (LGBT) rights group GLAAD welcomed Jenner's announcement.

"Though Jenner's journey is one that is deeply personal, it is also one that will impact and inspire countless people around the world," GLAAD head Sarah Kate Ellis said.

Singer Miley Cyrus gushed on Twitter: "I LOOOOVE LOOOVE LOOOVE Bruce Jenner!!!!!!!"

Born outside New York in October 1949, thrice-married Jenner became an American sports hero when he set a world record with his Montreal decathlon victory.

Leveraging his fame, he appeared on boxes of Wheaties, a popular American cereal known as "the breakfast of champions," then tried his hand as a movie actor, with less than stellar results.

But it was through his marriage to the former Kris Kardashian that he once again became a household name in "Keeping Up with the Kardashians" in which he appeared as the sometimes bemused stepfather of her flamboyant daughters Kourtney, Kim and Khloe.

The couple have two daughters of their own, but they obtained a divorce in December, 14 months after separating -- although he has been seen still wearing a wedding ring.

Hero once again

"Not only was I able to call him my husband for 25 years and father of my children, I am now able to call him my hero," Kris Jenner tweeted.

Jenner's 89-year-old mother Esther hailed her son's announcement, comparing her pride to that when he won at the Olympics.

"I never thought I could be more proud of you. But I'm learning I can be," she wrote.

Jenner's son Brandon tweeted simply: "Proud son," along with an Instagram picture of himself as a young boy perched on his smiling father's shoulders.

Step-daughter Kim Kardashian trumpeted:

"Love is the courage to live the truest, best version of yourself. Bruce is love. I love you Bruce.#ProudDaughter."

Her sister Khloe wrote: "Bruzer, I'm soooo proud of you! Dads really are heros."

National Center for Transgender Equality advocacy group executive director Mara Keisling called Jenner's declaration "one of the most profound displays of bravery and courage I've seen."

Jenner, clearly relieved to have finally come clean, said: "I'm saying goodbye to people's perceptions of me and who I am.

"I'm not saying goodbye to me because this has always been me."