Judge Ali al-Allush said on Tuesday the case had been put back to 15 November, but gave no further details.
His decision follows a weekend visit to Libya by Bulgarian President Georgi Parvanov to plead for the lives of the five convicted Bulgarian nurses and a Palestinian doctor.
The six were condemned in 2004 for injecting 380 children with blood transfusions infected with HIV, the virus that causes Aids. Forty-seven of those children have died.
Confessions under torture
The accused, who have spent six years in jail, maintain their innocence. Two nurses and the doctor initially confessed to charges, but later said police had extracted the confessions with torture, including beatings and electric shocks.
Washington and the European Union have been pressuring Libya over the case, which has strained relations between Sofia and Tripoli just as Muammar al-Qadhafi's government is returning to the international fold after years of isolation.
The defendants are relying on the testimony of Aids experts, who swore under oath that the children were infected due to poor sanitary conditions at the hospital.
However, the court in the Libyan town of Benghazi that condemned the health workers to death, rejected testimony from Luc Montaignier, the French doctor who first isolated the HIV virus, and Swiss and Italian colleagues, that the epidemic was due to a lack of hygiene.
AL-Qadhafi (L) met Parvanov (R)
ahead of Tuesday's court ruling
Instead, the court based its verdict on a report by Libyan experts that placed the blame on the foreign health workers.
Call for death penalty
At the weekend, Parvanov visited some of the children in hospital in the Mediterranean city of Benghazi where parents, waiting outside, called for the death penalties to be applied.
"I have come as a sign of solidarity with the children ... and to present European Union assistance to treat the children, so that a specialised hospital can be built in Benghazi," he told them.
In Tripoli, Parvanov met the five nurses and also held four hours of talks with Libyan leader al-Qadhafi to plead for the lives of the Bulgarians and the Palestinian.
Libyan Prime Minister Shukri Ghanem also met Parvanov and said the issue had to be treated "in a judicial and humanitarian context".
But he said: "This was a catastrophe and Bulgaria and the rest of the international community must understand the victims' families, who must not feel abandoned or ignored."
In December, Bulgaria refused an offer by Libya to free the nurses in exchange for the cash equivalent that Libya paid to victims of the airline attack over Lockerbie, Scotland, in 1988.