Amanda Knox, the American student accused of murdering Meredith Kercher, her British flatmate, claims she regrets having lied in police interviews to incriminate an innocent man.

Ms Knox, 21, said she was "afraid" but believes she will be acquitted in the end. On Tuesday Paoli Micheli, the pre-trial judge, ordered both her and Raffaele Sollecito, her former Italian boyfriend, to stand trial on December 4 on charges of murder, sexual assault and theft.

He sentenced Rudy Guede, an Ivory Coast immigrant and drifter, to thirty years in prison for the murder under fast track procedures, saying he accepted the "logic" of the prosecution allegation that all three took part in the murder and sex attack.

The judge refused a request by defence lawyers for Ms Knox and Mr Sollecito to be released and placed under house arrest while awaiting trial, ruling that they must stay in prison in case they flee or re-offend.

Mr Guede, who may be called as witness at the forthcoming trial, has said he saw a man "resembling" Mr Sollecito standing over Ms Kercher's body with a knife in his hand and heard Ms Knox's voice. Speaking while she waited for the ruling on whether she could leave prison for house arrest at a farm in Umbria run by a Catholic charity, Ms Knox said she was "very angry" with Mr Guede.

"Rudy's not telling the truth," she said. "He's made false accusations against me. I was not there, he's a liar. I hardly knew him, I only saw him three or four times and we've hardly ever spoken to each other." She said although the pre-trial hearings had ended in charges rather than an acquittal as she had expected, "I hope the next judge will believe what I say and not what other people say - starting with Rudy".

Ms Knox's remarks to her lawyers, Luciano Ghirga and Carlo della Vedova, and to Enrico Gasbarra, a Centre Left Parliamentary deputy, were reported today in Italian newspapers. Mr Gasbarra is studying conditions for women in Italian prisons.

He said Ms Knox was in a four bed, white-walled cell measuring four metres by five on the second floor of the prison outside Perugia, with one window. He said that as a joke one of the other inmates had remarked that the first time she saw Ms Knox she was not wearing underwear, to which Ms Knox had replied: "You were all so scandalised, but I didn't have any left".

She said the other women were "all like me, in here for the first time". Prison officials have said Ms Knox had "hardly slept" before Tuesday's verdict, and had cried herself to sleep. She had been comforted by the nuns who help to look after women prisoners, and who told her "you must be strong".

In what the US Democrat presidential nominee may regard as an odd endorsement, Ms Knox also said she would vote for Barack Obama as a "good American girl" because he "is on the side of the weak".

Ms Knox said she regretted she could not vote in the US election. "Oh, I'd really like that" she was quoted as saying. "I'm a good American girl and I feel it is my duty to vote." She said that her mother Edda Mellas also backed Mr Obama whereas her father, Curt Knox, was a John McCain supporter.

She said she was still fond of Mr Sollecito, who was "a sweet person", but "there is someone else I think of a lot, my boyfriend in America, David. He's been in China taking photographs and doing volunteer work. I always wear the clothes he sends me, especially one sweatshirt. When he writes he always wants to know what I'm reading so he can read the same book."

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