After refusing for weeks to negotiate with Libyan leader Moammar Gadhafi, the top representative of the rebel movement here offered a cease-fire if Gadhafi withdraws his forces from besieged Libyan cities and permits peaceful protests.

The offer came from Mustafa Abdul-Jalil, leader of the opposition national council, after meeting with a United Nations envoy to Libya, Abdelilah Al-Khatib.

There was no immediate response from the government in Tripoli, which has been distracted by defections of top regime officials. The government has announced purported cease-fires even while its forces have bombarded two western Libyan cities to put down rebellions and battled rebels in the east.

Jalil, who served as Gadhafi’s justice minister before defecting to the rebels, said the opposition will observe a cease-fire if “”the Gadhafi brigades and forces withdraw from inside and outside Libyan cities to give freedom to the Libyan people to choose, and the world will see that they will choose freedom.””

But Jalil reiterated that the opposition’s ultimate goal is to remove Gadhafi from power.

“”Our aim is to liberate and have sovereignty over all of Libya with its capital in Tripoli,”” he said.

Jalil indicated that the cease-fire offer was made in response to a U.N. request, which he said “”we have to respect.””

The cease-fire offer came as rebels continued Friday to battle government soldiers and militiamen for control of the strategic oil city of Port Brega, 140 miles west of the de facto rebel capital in Benghazi. Rebel forces retreated in chaos from the eastern edge of Port Brega after a sustained rocket barrage by Gadhafi forces.

Al-Khatib, the U.N. envoy, said the world body is seeking a cease-fire to protect civilians and he raised the issue with Gadhafi’s aides during a visit to Tripoli on Thursday. He said Gadhafi must pull his forces out of Libyan cities, according to the Al-Jazeera satellite channel.

Elsewhere in Benghazi, opposition leaders met in closed session for a second day Friday to try to settle a leadership dispute between two former Gadhafi military officers vying to lead rebel forces. Mustafa Gheriani, an opposition spokesman, said the council was determined “”to settle this matter.””

Gen. Abdul Fatah Yunis, a former interior minister and ex-commander of the special forces, has been challenged by another former Gadhafi confidante, Khalifa Hefter. Hefter is a former Libyan army officer who broke with Gadhafi more than 20 years ago and moved to the U.S. before returning to Libya about two weeks ago.

Zahi Mogherbi, a retired political science professor who advises the opposition national council, said the rivalry between the two officers has undermined the rebel effort and needs to be resolved.

“”Something has to be done, and I think the council will make a decision soon,”” Mogherbi said Friday. “”These two have shown they cannot work together.””