A fourth promo video has been released ahead of the highly anticipated Bruce Jenner interview with Diane Sawyer.

The former Olympian is expected to talk about his gender transition in the ABC special which airs on 24 April.

The 30-second clip shows the 65-year-old welcoming Sawyer into his home. The Keeping up with the Kardashian star's sense of trepidation is palpable as he says: "It's going to be an emotional rollercoaster, but somehow I'm gonna get through it."

In another snippet from the interview, Jenner expresses concerns for his family saying: "I can't let myself hurt them. They're the only ones I'm concerned with."

I wanna know how this story ends, you know? How does my story end?
- Bruce Jenner

The video includes footage of Bruce's older children, Burt, 36 and Casey, 34, from his marriage to Chrystie Crownover and his sons Brandon, 33, and Brody, 31, from his marriage to Linda Thompson.

In another sequence, a photograph shows Jenner with daughter Kendall, 19, and Kylie, 17, and stepdaughters Kourtney, 36, Kim, 34, and Khloe. 30.

In the interview Jenner is expected open up about how he first broke the news to this family that he is undergoing gender reassignment and their reaction. Some of the children are also expected to be interviewed for the documentary.

The promo concludes with Jenner's poignant comment: "I wanna know how this story ends, you know? How does my story end?"

The interview, which has been shrouded in secrecy was conducted in February, with Sawyer spending a day with Jenner in Los Angeles, and a second day in New York.

He has never responded to the transgender rumours, despite his increasingly feminine appearance and reports that he has undergone surgery including breast implants. Speculation as to his changing appearance first mounted after he reportedly had his Adam's apple surgically reduced, a common procedure often undertaken by men seeking gender reassignment. The 65-year-old reality star also allegedly started taking oestrogen and underwent a series of physical changes, growing his hair long, sporting hot pink nails and appearing with clean shaven legs.

Supporters of the star took to Twitter to express their outrage after paparazzi photos were published by The New York Daily News allegedly of Jenner wearing a dress.

The one-time athlete is said to be taking legal action for intrusion of his privacy.

While he has won widespread support from fans and fellow celebrities for his courageous decision to open up about his personal life, the announcement has come as a shock to his ex-wife Kris Jenner. The Kardashian matriarch is believed to have been blind-sided by the revelations that her husband of 22-years has decided to live as a woman.

Jenner was also the subject of mocking emails sent by director Cameron Crowe to former Sony Pictures studio head Amy Pascal. The offensive comments emerged after thousands of leaked emails were published on Wiki leaks.

Meanwhile, the ABC special is expected to win record ratings become one of the top 100 , most watched broadcast in the US ever.

Oprah Winfrey's 1993 interview with Michael Jackson, in which the singer opened up about his abusive childhood and confronted rumours about his lifestyle. The interview was watched in 36.6 million homes. It was one of the biggest interviews in TV history and one of the most watched telecasts of all time in the U.S.

Barbara Walters' 1999 interview with Monica Lewinsky was seen in 33.2 million homes.

Bruce Jenner The Interview airs on ABC on Friday 24 April at 9/8C.