The cleric Abu Omar says he was kidnapped and then tortured in Egypt
An Italian judge has ruled that the trial of Americans and Italians suspected of abducting an Egyptian imam should go on but with restrictions.
The ruling follows a ban by the Italian Supreme Court on the use of classified evidence in the proceedings.
The ruling is a blow for defence lawyers, but is also likely to exclude much of the evidence on which the prosecution has built its case.
This is the first trial over the CIA's "extraordinary rendition" programme.
Under the secretive practice, suspects were transferred overseas for interrogation.
Many, including Abu Omar, say they were then tortured and held without charge.
Abu Omar - whose real name is Hassan Mustafa Osama Nasr - was kidnapped in daylight on a Milan street in 2003.
Prosecutors then say he was flown to Germany, and then Egypt, where he was held for years until being released without charge.
Two years ago 26 Americans and seven Italians - alleged intelligence agents - went on trial, accused of jointly orchestrating the kidnapping.
The Americans are being tried in absentia after their government refused extradition requests, and the trial has been beset by legal challenges.
The Italian government, which has supported the US's "war on terrorism", but says it had no involvement in Abu Omar's abduction - has tried to have the case thrown out, claiming some of the evidence was classified, and in March the Supreme Court agreed.
Challenge for prosecution
On that basis, defence lawyers argued that the whole case should be thrown out, but on Wednesday Judge Oscar Magi ruled the case should continue, but with classified evidence withheld.
The ruling was celebrated as "positive" by prosecutor Armando Spartaro, though he told Reuters news agency that the secrecy restrictions would "obviously involve a big effort from the prosecution in gathering evidence in future".
But Titta Media, one of the defence lawyers, said the trial was now "at a dead end. It is only going ahead to save face," she was quoted as saying by Reuters.