Amanda Knox may return to Italy for a murder retrial, she said as she launched a memoir about her nightmare, including frank details about sex, drugs and her harrowing time behind bars.

In interviews to promote the book - which also recounts how she considered suicide in jail - she said she hoped her slain former roommate Meredith Kercher's family will read it, although she has had no contact with them.

"It matters to me what Meredith's family thinks I really hope the Kerchers read my book. And they don't have to believe me. I have no right to demand anything of anyone. But I hope they try," she told USA Today.

Amanda Knox (left) speaks to Diane Sawyer in New York during an interview on Tuesday on the ABC television network. Provided by Reuters

"I want them to know, their grief has my every respect, has the respect of my family," she told ABC television, in her first broadcast interview since her release two years ago.

The US student and her former Italian boyfriend Raffaele Sollecito were sentenced to 26 years and 25 years in prison for the killing of Kercher six years ago, allegedly in a drug-fuelled sex attack.

She was acquitted on appeal and released in 2011, returning to her native Seattle. But in March, Italian authorities overturned that judgment, and ordered the 25-year-old to stand trial again.

Although most legal analysts expect Knox to be tried again in absentia following the decision, she told USA Today in an interview she is considering returning to Italy.

Knox has launched a publicity campaign in the United States to promote her autobiography Waiting to be Heard for which she was reportedly paid a $3.8 million advance.

In the 480-page book, she describes her early life in Seattle and her decision to take a year out to live in the small Italian city of Perugia to learn Italian language and culture.

She is open about her attitude to sex, and how it was changing as she headed overseas. She had had sex with four men before her departure.

"I left for Italy having decided I needed to change that. For me, sex was emotional, and I didn't want it to be anymore.

"I hated feeling dependent on anyone else. I wanted sex to be about empowerment and pleasure, not about 'Does this person like me? Will he still like me tomorrow'?"

She moved in with two Italian girls and Kercher, who was also a foreign student, and led an easy-going life with a group of boys who lived downstairs in the same house.

"Around our house, marijuana was as common as pasta," she wrote, while describing in detail a number of sexual encounters before she met Sollecito, a week before the murder.

She also recounts the day Kercher's body was found that police rapidly became suspicious. In one early interrogation she reports being slapped around the head while being told "Stop lying".

Knox was eventually charged, tried and sent to prison, where she describes repeated sexual harassment and detailed thoughts of suicide, for example in the shower, where "steam would fog up the guard's viewing window".

"I imagined cutting both my wrists and sinking into oblivion in a calm, quiet, hot mist," she writes.

In an interview with ABC News anchor Diane Sawyer, Knox - wearing a sleeveless dress, small pearl earrings and hardly any makeup - said she wanted to clear her name, both legally and in terms of her public reputation.

She said she was aware of being labeled a seductress, a she-devil and other names in the media, but she said, "They're wrong."

AFP-AP