Families of the victims are seeking a total of 4.3 billion euros in what they see as compensation, a definition rejected by Bulgaria which says the nurses are not guilty of infecting the children.
Charitable organisations from Libya, the European Union, United States, and Bulgaria are all taking part in the Benghazi International Fund set up in the Libyan capital, Tripoli, on Saturday.
Speaking to Aljazeera, Idriss Lagha, a spokesman for the families, said the agreement had been concluded but further talks were needed.
"An official agreement has been wrapped up on the establishment of the fund which will only be operational after negotiations end on the demands of the victims' families," he said.
The announcement follows a 25 December verdict by the Libyan supreme court ordering a new trial for the five Bulgarians and a Palestinian doctor who have already spent seven years in prison.
The six were originally sentenced to death after being found guilty by a court of transfusing 426 Libyan children with blood contaminated with the HIV virus in a Benghazi hospital. Fifty-one of the children have since died.
Lagha added: "The demands centre on compensation of 10 million euros for each victim and a medical follow-up in Libya and abroad.
"If we reach an agreement, the fund will then be operational but if not, it will be considered void."
Kalfin (L) said Bulgaria would
not pay compensation
Talks to fix the fund's capital will resume on 13 February, Lagha said.
Earlier this month, Ivaylo Kalfin, the Bulgarian foreign minister, told a press conference in Sofia: "Bulgaria will not participate with any resources like compensation ... because the Bulgarian nurses are not guilty."
He added: "Like other European countries, we will train medical workers and supply aid for the treatment of the infected children."
Officials from the fund met the victims' families, who want compensation, said Maxim Minchev, a member of a Sofia-based NGO that helped found the Benghazi International Fund.
"At the meeting, the families raised their request and demanded 10 million euros per child in compensation, but no agreement has been reached to that end," Minchev quoted the Gaddafi Foundation, which hosted the talks, as saying in a statement.
Libya has suggested that, under Islamic law, the charges against the nurses could be dropped if Bulgaria pays "blood money" to the families.
But Bulgaria and its allies insist the nurses are innocent, saying they were tortured to confess to the crime and that the epidemic started in the Benghazi hospital before they began working there.
Sofia has called the aid fund a voluntary, not a political or diplomatic, initiative and has rejected contributing to any type of compensation as a false admission of guilt.