“One of the scenarios effectively envisaged is that he stays in Libya on one condition, which I repeat: that he very clearly steps aside from Libyan political life,” Mr. Juppé said on the French television channel LCI. “A cease-fire comes about by a formal and clear commitment by Qaddafi to give up his civil and military responsibilities.”

In Washington, an Obama administration spokesman did not disagree with Mr. Juppé’s remarks on Colonel Qaddafi. “He needs to remove himself from power — and then it’s up to the Libyan people to decide,” the spokesman, Jay Carney, told reporters when asked about the French position.

Western officials who met last Friday in Istanbul agreed that they must devise a set of negotiating principles. They have agreed that military pressure will be maintained until Colonel Qaddafi agrees to a cease-fire and to give up all power. Then some form of national reconciliation government should be established to create a new Libyan leadership, which is supposed to be responsible for what happens next to Colonel Qaddafi.

The colonel’s calculations are complicated by a warrant for his arrest on war-crimes charges issued by the International Criminal Court in The Hague. Some members of the anti-Qaddafi coalition are more willing than others for the colonel and his family to remain in Libya, but the colonel is also bound to see the circumstances of the former Egyptian president, Hosni Mubarak, as a warning. Mr. Mubarak gave up all power but was later arrested, with his sons, by the transitional, military-led government. The Misurata delegation — Mr. Fortia, who is the city’s representative on the rebel National Transitional Council; three men described as rebel military leaders in the city, Gen. Ramadan Zarmuh, Col. Ahmed Hashem and Col. Brahim Betal Mal; and two other members of Misurata’s “city council” — said that Mr. Sarkozy had been supportive.

“To get help, there must be coordination,” Mr. Fortia said later at a news conference. “France helps us in many domains.”