Intense fighting in the besieged Libyan city of Sirte has kept provisional government fighters from advancing in one of the few remaining strongholds of former leader Moammar Gadhafi's supporters.

National Transitional Authority forces say they have captured the city's port, but Gadhafi loyalists still control most of Sirte.

NATO said Tuesday about 200,000 civilians, mainly in Sirte and Bani Walid, are still threatened by pro-Gadhafi forces.

Earlier Tuesday, NTC fighters and elders from Mr. Gadhafi's tribe were trying to negotiate a truce that would allow safe passage for families trying to leave Sirte.

Meanwhile, a White House spokesman said the United States is working with the NTC to help secure weapons stockpiles in Libya. Jay Carney said a State Department official is in Libya working with provisional leaders to develop a program for controlling and destroying shoulder-fired anti-aircraft missiles. He also said the U.S. is working with NATO to provide the NTC with all known locations of weapons.

Also Tuesday, Tunisian appeals court has overturned an illegal entry conviction against former Libyan Prime Minister Baghdadi Mahmudi.

Judicial officials dismissed the charges against the Gadhafi-era minister.

Last week, a Tunisian court sentenced Mr. Mahmudi to six months in prison on the illegal entry charges. Tunisian officials said Tuesday that they had not received an extradition request from Libya.