An Italian judge has decided that Premier Silvio Berlusconi will be called to testify in the trial of 26 Americans and several Italians charged with kidnapping a terror suspect during a CIA operation.
Judge Oscar Magi approved the defence request as the case resumed today.
He also ruled that former premier Romano Prodi will be called to give evidence.
Mr Berlusconi, who has just been re-elected for another term, is considered a key witness because he was premier when Egyptian cleric Osama Moustafa Hassan Nasr disappeared in February 2003.
Italian prosecutors say Nasr, also known as Abu Omar, was abducted as part of the CIA’s extraordinary rendition programme.
The CIA has declined to comment on the case.
Mr Berlusconi's testimony had been requested by the lawyers of Nicolo Pollari, a former intelligence chief who is one of the defendants in the case.
Pollari hopes the evidence might help prove that he was against the rendition, lawyers said.
He could face from one to 10 years in jail if convicted.
Italian prosecutors say the cleric was transferred to US bases in Italy and Germany before being moved to Egypt, where he was imprisoned for four years.
Nasr, who was released last year, claims he was tortured.
All but one American suspect in the case have been identified by prosecutors as CIA agents.
They are being tried in absentia.