LISBON, Portugal (AP) — Portugal's Supreme Court has rejected a former CIA operative's appeal against extradition to Italy to serve a six-year sentence for her part in the U.S. extraordinary renditions program, a court official said Monday.

The official told The Associated Press that Sabrina De Sousa's only remaining recourse to avoid being sent to Italy would be to appeal to Portugal's Constitutional Court, arguing her extradition order is unconstitutional. The official spoke on condition of anonymity in accordance with court rules.

De Sousa's Portuguese lawyer, Manuel Magalhaes e Silva, did not immediately respond to an emailed request for comment. Her Italian lawyer, Dario Bolognesi, said he is hopeful of obtaining clemency from Italy's president.

De Sousa, who was working in Italy under diplomatic cover, faces prison for her role in the 2003 kidnapping in Milan of Osama Moustafa Hassan Nasr, a terror suspect who was under surveillance by Italian law enforcement at the time. De Sousa was among 26 Americans convicted in absentia in the case, which also implicated Italy's secret services and has proven embarrassing to successive Italian governments.

The extraordinary rendition program was part of the anti-terrorism strategy of the U.S. administration following the Sept. 11 attacks. Years later, President Barack Obama ended the program.

A lower Lisbon court ruled in January that De Sousa should be turned over to Italy following her arrest at Lisbon Airport in October on a European warrant. Authorities seized her passport while awaiting the court decision on her extradition.

De Sousa, who was born in India and holds both U.S. and Portuguese passports, has said that she had been living in Portugal and intended to settle there. She was on her way to visit her elderly mother in India with a roundtrip ticket when she was detained.

Bolognesi, her Italian lawyer, told the AP he has been meeting and will continue to meet with officials to explore the possibility that President Sergio Mattarella, Italy's head of state, could lower her sentence to the point she would be eligible in Italy to do social services instead of prison time.

He noted that other convicted defendants have benefited from presidential clemency. In December 2015, Mattarella shaved two years off the sentence of a former CIA base chief, Robert Seldon Lady. Mattarella also wiped out the entire three-year penalty for another American convicted in the case. Others convicted in the case have requested clemency, according to Italian officials.

Both Mattarella and his predecessor, Giorgio Napolitano, have cited Obama's decision to end extraordinary rendition as their motive for granting reprieves.

Frances D'Emilio in Rome contributed to this report.