The delegation, which arrived in Tripoli on Sunday, includes the European Union commissioner for foreign affairs, Benita Ferrero-Waldner, and chief French presidential aide Claude Gueant.

Talks Monday continued late into the night, said Emmanuel Altit, a Paris-based lawyer for the nurses.

"We hope that whatever happens tonight -- to be clear, if she leaves alone or with the nurses -- this visit will help contribute to finding a solution," he said.

France was seeking the "immediate" return home of the six -- in jail for the past eight years -- in a final goodwill gesture by Libya after it commuted the death sentences of the six in favor of life in prison.

President Nicolas Sarkozy was to visit Libya on Wednesday -- if the Bulgarians were freed, Libyan officials said, speaking on condition of anonymity. The Web site of the French news weekly Le Point, which broke news of the mission, said that Sarkozy's visit to Tripoli was conditional on the return of the prisoners.

Bulgaria made an official request Thursday for Tripoli to repatriate the medics to serve their sentences in Bulgaria. It granted citizenship to the Palestinian doctor, Ashraf al-Hazouz, last month.

In a phone conversation with Sarkozy, Bulgarian President Georgi Parvanov "expressed appreciation for the active role and the personal engagement of Mrs. Cecilia Sarkozy and the European commissioner in charge of foreign affairs, Benita Ferrero-Waldner, for solving the case," his office said.

Sarkozy spoke several times by phone with Libyan leader Moammar Gadhafi and European Commission President Jose Manuel Barroso, as well as with Parvanov, his office said.

This was the French first lady's second trip to Libya on behalf of the prisoners, and, like the first trip, it drew criticism from the rival Socialist camp with one lawmaker charging that the president, in office since May 16, was profiting from the work of other nations, and the EU, which have worked on behalf of the nurses for years.

"What I know is that this is very, very tough. This has lasted eight and a half years," the French president said Monday.

Cecilia Sarkozy has the "role of an intermediary" in the affair, said Roger Karoutchi, minister in charge of parliamentary relations. "It is not a diplomatic role in the classical sense," Karoutchi said on the iTele TV station. "She wants to take part in a human, humanitarian, social action."

Sarkozy talked on Monday by phone with European commission President Jose Manuel Barroso about the timetable for the release of the prisoners and their "immediate" return home, a statement from the French president's office said.

Libyan officials said Cecilia Sarkozy met with Gadhafi on Sunday. The officials, who spoke on condition of anonymity because of the sensitivity of the talks, would not elaborate.

Bulgarian Foreign Minister Ivailo Kalfin said in Brussels Monday that the delegation was hoping to finalize talks with the Libyans and expressed hope a deal was on the horizon.

"We are at the stage now where the decision is clearly political," Kalfin said. "I hope there will be enough goodwill from the Libyan side today."

Cecilia Sarkozy and Gueant made an initial trip to the country on July 12, meeting with Gadhafi and the medics. They also met with some of the infected children, their families and the prisoners.

In Paris, the opposition Socialist Party looked askance at the trip, with lawmaker Pierre Moscovici contending the diplomatic initiative was "largely a show" by conservative Sarkozy, who was looking to profit from the work over the years of Britain, Germany and the European Union and appropriate any success.

Libya accused the six of deliberately infecting more than 400 Libyan children with HIV. The medics, jailed since 1999, deny infecting the children and say their confessions were extracted under torture.