David Marriott said Knox had never agreed to attend, and there's "no requirement she be there." Still, there remains the possibility that Italy could request her extradition from the United States.
In an interview with CNN's Chris Cuomo in May, Knox said she "didn't know" whether she'd return. It's a really complicated question," Knox said. "I mean, I'm afraid to go back there. I don't want to go back into prison."
Knox spent several years behind bars in Italy, after she was convicted in 2009 of murdering 21-year old British exchange student Meredith Kercher.
Kercher was found stabbed to death in November 2007 in the villa she rented with Knox, then 20, in the central Italian university town of Perugia.
The convictions of Knox and her ex-boyfriend, Raffaele Sollecito, were overturned in 2011 for "lack of evidence."
After her acquittal, Knox returned to her hometown of Seattle, Washington, where she has been living since.
Italians ask: Can Americans get away with murder?
Italy's Supreme Court decided last year to retry the case, saying the jury that acquitted Knox didn't consider all the evidence, and that discrepancies in testimony needed to be answered.
The high court also said evidence could support prosecutors' initial argument -- that Kercher was killed in a twisted sex misadventure game, according to Italian news agency ANSA.
Knox says such claims were "a bombardment of falsehood and fantasy."
Timeline of the murder case
"No one has ever claimed that I was ever taking part in deviant sexual activity. None of my roommates, none of my friends, none of the people who knew me there. This is simply coming out of the prosecution," she told CNN in May. "I was not strapping on leather and bearing a whip. I have never done that. I have never taken part in an orgy. Ever."
Knox and Sollecito's retrial, which is expected to start this fall, should examine discrepancies in testimony, the high court said. These include differing witness accounts of when screaming could be heard from the home, ANSA reported.
Knox may be ordered to return to Italy for the retrial. If she refuses, the Italian government could appeal to the United States for her extradition. But even if it does, it's not clear whether the United States would extradite Knox.
