In March, Italy's supreme court ordered a new trial for Knox and her former Italian boyfriend for the slaying of Meredith Kercher in Perugia, where they were students.
An appeals court in 2011 had acquitted both, overturning convictions by a lower court. The new appeals trial begins in Florence on Sept. 30.
Florence daily La Nazione quoted lawyer Luciano Ghirga Saturday as saying he recently met with Knox and fellow defense team members in the U.S., and that Knox confirmed what her lawyers said right after the supreme court ruling - she won't return to Italy for the new trial.
In ordering the new trial, Italy's high court harshly faulted the appeals court that acquitted Knox of murdering her roommate, saying its ruling was full of "deficiencies, contradictions and illogical" conclusions. It ordered a new appeals court to consider all the evidence to determine whether Knox helped kill the young woman.
Among the undervalued pieces of evidence was Knox's own statement to police, written in English after her police interrogation, in which she wrote that while she couldn't remember clearly, she had an image of herself in her apartment kitchen with her hands covering her ears to drown out Kercher's screams.
Kercher's body was found in November 2007 in her bedroom of the house she shared with Knox in Perugia, a central Italian town popular with foreign exchange students. Her throat had been slashed.
Knox, now 25, and her Italian ex-boyfriend, Raffaele Sollecito, 29, were initially convicted of the crime and sentenced to long prison terms. A Perugia appeals court acquitted them in 2011, criticizing virtually the entire case mounted by prosecutors. The appellate court noted that the murder weapon was never found, said that DNA tests were faulty and that prosecutors provided no murder motive.
Both Knox and Sollecito denied any involvement, saying they weren't in the apartment at the time.
A young man from Ivory Coast, Rudy Guede, was convicted of the slaying in a separate proceeding and is serving a 16-year sentence.