Rome ? Italy’s government denied Thursday it had prior knowledge of the alleged CIA kidnapping of a radical Egyptian cleric and summoned the U.S. ambassador to explain the operation, which has led prosecutors to seek the arrest of 13 purported CIA officials.

The rare public challenge by an allied country to the CIA’s “extraordinary rendition” program for suspected terrorists threatened a new jolt to relations with Washington, recently strained by the killing of an Italian agent by U.S. soldiers in Iraq.

Carlo Giovanardi, minister for relations with parliament in Premier Silvio Berlusconi’s government, addressed the legislature in response to opposition demands that Italy say whether authorities knew of plans to kidnap the Egyptian, considered an Islamic terrorist.

Italian prosecutors have accused the 13 CIA officials of kidnapping Osama Moustafa Hassan Nasr, known as Abu Omar, in Milan on Feb. 17, 2003, and sending him to Egypt, where he reportedly was tortured.

The Egyptian purportedly was seized as part of the CIA’s program in which suspected terrorists are transferred to third countries without court approval, where they face interrogation and possible torture.

Giovanardi said the alleged operation was never “brought to the attention of the government of the republic or national institutions,” an apparent reference to Italy’s intelligence agencies.

Therefore, he said, “it is not even possible” that Italy ever authorized such an operation.

Prosecutors have said they are preparing extradition requests for the 13 CIA officials and have asked Interpol for help in tracing the suspects, all identified as U.S. citizens.

On Thursday, the CIA again declined to comment on developments in the case.

Nasr told his wife in an intercepted cell phone call from Egypt that he was tortured, the Milan prosecutor’s office has said. He reportedly was hung upside down and subjected to extreme temperatures and loud noise that damaged his hearing.

The U.S. Embassy in Rome, the CIA in Washington and Egyptian officials have declined comment.