The imprisonment of the medics caused an international outcry
An EU delegation is in the Libyan capital, Tripoli, aiming to broker a deal to free the five Bulgarian nurses and a Palestinian doctor.
The six, who have always denied the charges, had death sentences commuted to life in prison last week.
Libya is also said to be seeking more funds to treat the infected children.
The government in Bulgaria wants the medics to be allowed to return home.
But the EU is reported to be unwilling to agree any compensation deal that appears to gives the impression that it accepts the six medics are guilty.
'Very tough'
Cecilia Sarkozy, the wife of French President Nicolas Sarkozy, is in Tripoli accompanying the EU's external relations commissioner, Benita Ferrero-Waldner.
She is said to have met Libyan leader Muammar Gaddafi on Sunday evening.
TRIAL IN DATES 1999: 19 Bulgarian medics and a Palestinian doctor are arrested at a Benghazi hospital after an outbreak of HIV/Aids among children. 13 are later freed May 2004: Libya convicts and sentences five Bulgarian nurses and the Palestinian doctor for infecting children with HIV. A Bulgarian doctor is freed Dec 2005: Libyan Supreme Court overturns the convictions and orders a retrial Dec 2006: Medics sentenced to death a second time Feb 2007: Medics appeal to the Libyan Supreme Court June 2007: Top EU officials hold talks in Libya to try to secure medics' release 11 July 2007: Libya's Supreme Court upholds death sentences
Profile of the medics Timeline: Medics trial
Mr Sarkozy was also reported to be closely involved in efforts to free the six, despite some criticism from domestic opponents, who accused him of effectively hijacking years of patient work by other EU nations.
"What I know is that it's very tough. This has been going on for eight-and-a-half years," Mr Sarkozy said in France.
But Bulgaria's Foreign Minister, Ivailo Kalfin, speaking in Brussels, told the AFP news agency that the decision on whether to free the six was now "purely political".
"If the Libyans show goodwill enough, the transfer can be done very quickly."
Bulgaria has granted citizenship to the Palestinian doctor so that he may also benefit from any deal to transfer the medics to Bulgaria.
The six have been imprisoned in Libya since 1999, after being accused and then convicted of deliberately spreading HIV in a children's hospital. They say torture was used to extract their confessions.
Foreign experts say the infections started before the medics arrived at the hospital, and are more likely to have been a result of poor hygiene.
Last week, Libya lifted the death sentence for five Bulgarian nurses and a Palestinean doctor in the case about the HIV infection of hundreds of Libyan children. The deal called for a US$460 million settlement for the families of the children.

However, now Libya is holding out for a better deal. According to reports, Libya is seeking more money for the treatment of the children, as well as normalized relations with the European Union. Another sticking point in making a deal has been that Bulgaria and the EU are unwilling to strike any deal that admits the guilt of the medics, whose innocence they insist upon.
Ivaylo Kalfin
Bulgarian Foreign Minister Ivailo Kalfin spoke to reporters in Brussels. "We are at the stage now where the decision is purely political," he said. "I hope there will be enough will from the Libyans' side today in order to finalise talks ... If they show this will, then the transfer can be done very quickly."

"Allow me not to go into any details because that would make all the efforts that are being made in Libya right now meaningless," Kalfin was quoted to have said later in the day, according to Bulgarian national television.