But Carr said he expected Taylor to remain in custody for the foreseeable future.
"I think, and I regret to have to say it, but they [Libyan authorities] will need some time to work this through their political system," he told ABC television.
Negotiations are complicated by tense relations between Libya's transitional Government and the Zintan militia.
The letter obtained by the Guardian supports Libyan belief in Taylor's alleged role in clandestine communications between Saif and former members of his late father's regime.
Taylor and her ICC colleagues met Saif to discuss the appointment of defence counsel for his proposed trial on charges of crimes against humanity, but the Libyan letter to UN Security Council president Li Baodong claims she had committed "blatant violations" of her role.
These included the smuggling of spying devices and a coded letter from Mohammad Ismail, Saif's "main aide" and an associate of Gaddafi's intelligence chief Abdullah al-Senussi, the Guardian reported the Libyan letter as saying.
The letter said Taylor had smuggled a sophisticated miniature "video camera pen" and a watch that "functions for the same purpose", in clear violation of Libya's judicial rules and the moral and professional commitments of the ICC.
"During the meeting, Ms Taylor handed over to the accused [Saif] documents which content [sic] constitutes a threat to the Libyan national security, in the presence of an interpreter," the Guardian quoted the letter as saying.