"It would be a political exit that would remove Gaddafi and his family from the scene," and allow the "a government of national reconciliation," to take over, Frattini said in an interview on Italian television.
Possible members of Gaddafi's government who could take part in the new government "have already been identified," he said.
He said unveiling the plan still being worked out together with the United Nations could cause it to fail.
Separately, the chief prosecutor at the International Criminal Court on Monday is due to ask judges in The Hague to issue arrest warrants for three senior members of the Libyan regime.
One warrant is expected to be issued for Gaddafi.