A former CIA agent said Wednesday she will be extradited to Italy to serve a prison sentence for her part in the U.S. extraordinary renditions program after Portugal's Constitutional Court rejected her final appeal.

Sabrina de Sousa told The Associated Press she is waiting to be told when she will be taken to Italy, where she was convicted in absentia and has a four-year sentence to serve.

Since her October arrest in Lisbon on a European arrest warrant, De Sousa has lost her extradition fight at a lower Lisbon court and her appeal of that decision to the Portuguese Supreme Court.

De Sousa was among 26 Americans convicted for the kidnapping of terror suspect Osama Moustafa Hassan Nasr, also known as Abu Omar, from a Milan street on Feb. 17, 2003. She insists she wasn't involved in the abduction.

The Constitutional Court said in a ruling posted on its website late Tuesday that De Sousa's appeal was rejected.

Under Portuguese legal procedure, the Constitutional Court now sends its decision back to the lower court. That court then informs the police, who set in motion the extradition process in conjunction with Italian authorities.

De Sousa said in an email to the AP that she had "no idea" when she might be sent to Italy.

Her Italian lawyer has previously said he is hopeful of obtaining clemency from Italy's head of state in the case, which has also implicated Italy's secret services and proven embarrassing to successive Italian governments. President Sergio Mattarella has granted clemency to other defendants convicted in the case.

De Sousa said she sent Wednesday a letter to Pope Francis, through the Vatican's embassy in Lisbon, urging him to speak out against the extraordinary renditions used by the CIA after the Sept. 11, 2001, attacks. The pontiff has already condemned the practice, in a 2014 speech.

De Sousa, who has both U.S. and Portuguese citizenship and was working in Italy under diplomatic cover, argues that she was never officially informed of the Italian court conviction and couldn't use confidential U.S. government information to defend herself.

"I was never notified nor was I allowed to defend myself because of secrecy obligations," she wrote in the letter to the pope. "The absence of due process and the imposition of various versions of state secrets are obstacles that prevent the many unanswered questions about the premise and justification for Abu Omar's rendition."

The rendition program, under which terror suspects were kidnapped and transferred to centers where they were interrogated and tortured, was part of the anti-terrorism strategy of the U.S. administration following the attacks. President Barack Obama ended the program years later.