In a case testing Italian-U.S. relations, a Milan prosecutor sought arrest warrants Wednesday for six more purported CIA (search) operatives, accusing them of helping plan the kidnapping of an Egyptian radical Muslim cleric.

An Italian court has already issued warrants for 13 purported CIA officials accused of helping carry out Osama Moustafa Hassan Nasr's (search) 2003 abduction.

But the court initially turned down a request to issue arrest warrants for the six who prosecutor Armando Spataro (search) says helped plan the abduction.

The court is expected to rule in the next few days on his appeal, Spataro said.

Cell phone tracking shows the six made nearly 100 inspections of the Milan area where the cleric was seized, and that they studied his habits as well as the best routes to the highway used to bring the Egyptian to Aviano, a joint U.S.-Italian air base north of Venice, according to the prosecutor's request, obtained by The Associated Press.

"There were no doubts" the six were part "of a single group of Americans who came to Milan to carry out the operation," the prosecutor said in his appeal.

Nasr, known as Abu Omar, was allegedly snatched on a Milan street on Feb. 17, 2003, flown from Aviano to Ramstein (search) air base in Germany and then to Egypt, where he reportedly was tortured.

The operation purportedly was part of the CIA's "extraordinary rendition" program, in which terror suspects are transferred to third countries without court approval, subjecting them to possible ill treatment.

The court-appointed lawyer for the six, Guido Meroni, said there was no proof of his clients' direct participation in the alleged kidnapping.

The CIA has declined to comment on the case, which has strained relations between the two allied nations. Premier Silvio Berlusconi (search) has a close relationship with President Bush, but ties between Rome and Washington were previously jolted by the shooting death of an Italian agent by U.S. troops in the Iraqi capital, Baghdad, in March.

Italy's magistrates are fiercely independent of the government.

After initial outrage in Italy, Berlusconi told the U.S. ambassador he expects Washington to "fully respect Italian sovereignty."

The government also denied in parliament that any Italians were involved, dismissing a Washington Post report quoting unidentified CIA veterans claiming the CIA station chief in Rome had briefed an Italian official before the operation.

In its appeal, the prosecution repeated its contention the abduction was a grave violation of Italian sovereignty and that it damaged an Italian anti-terrorism operation.

Nasr was believed to have fought in Afghanistan and Bosnia and prosecutors were seeking evidence against him before his disappearance, according to Italian news reports last year, which cited intelligence officials.

None of the suspects is believed to be in Italy. After the initial arrest warrants, prosecutors said they would seek extradition.

While the Italian government has appeared to try to contain any damage, some media have started focusing on the large U.S. military presence in Italy, where key Navy, Air Force and Army installations have been generally taken for granted over the years.

Germano Dottori, a political analyst at the Center for Strategic Studies (search) in Rome, said the Milan case could damage cooperation between the two countries' secret services.

"Among U.S. intelligence officers you might see a reduced trust in their Italian counterparts," he said. "Cooperation between secret services requires trust, often on a person-to-person basis. If one is afraid that in the future his identity will be revealed, he'll think twice before cooperating with someone."

Dottori added he hoped the incident would be put aside quickly, as the current threats of terror attacks in Europe and Italy "require maximum vigilance and cooperation."