Fugitive strongman Moamer Gaddafi denounced Libya's new leadership as a "charade" backed by Nato air strikes which will not last forever, in an audio message aired on television on Tuesday.
The remarks came ahead of the first talks between US President Barack Obama and Mustafa Abdel Jalil, the head of the National Transitional Council (NTC) -- now recognised as Libya's legitimate leaders.
"What is happening in Libya is a charade which can only take place thanks to the (Nato-led) air raids, which will not last forever," said Gaddafi, for decades an outlandish fixture at the annual UN General Assembly in New York with his tent and rambling speeches.
Gaddafi is believed to be hiding in Libya, although members of his family fled to Algeria and Niger after rebel fighters, backed by a Nato-led air war, overran Tripoli on August 23.
"Do not rejoice and don't believe that one regime has been overthrown and another imposed with the help of air and maritime strikes," Gaddafi said in the message broadcast on Syria-based Arrai television.
The recording was the first since September 8 by Kadhafi, who is wanted for alleged crimes against humanity along with his son Seif al-Islam and intelligence chief Abdullah al-Senussi.
It was released after the new regime's forces said they captured the airport and a garrison in his southern redoubt of Sabha, and fighting raged in two of his northern strongholds.
The capture of the airport and garrison at Sabha, a strategic desert city 800 kilometres (500 miles) south of Tripoli, was announced early Tuesday by Mohammed Wardugu, spokesman for the NTC's "Desert Shield Brigade."
NTC forces were set to take total control of the entire region "imminently," said Wardugu, brother of brigade commander Barka Wardugu.
"The problem is southwestern Libya, most notably Awbari and Ghat (on the Algerian border), which are still under the control of Gaddafi forces," he said adding they included some "important commanders."
He said NTC forces had also seized Kadhafi's intelligence chief in the Al-Kufra region in the deep southeast, General Belgacem Al-Abaaj, and forced more than 300 of his mercenaries to flee before detaining 150 loyalists.
"Our fighters ambushed then and killed, wounded or captured many," Wardugu said without giving figures.
Nato said it had targeted Sabha with air strikes on Monday, taking out two air missile systems, two radar defence facilities and three air missile facilities.
It also struck an armed vehicle and multiple rocket system in Sirte; six anti-aircraft guns and a command and control node around the Al-Jufra oasis towns of Waddan and Hun; and another command and control node near Bani Walid.
The Nato strikes around Sirte came as dozens of new regime fighters stormed the nearby town of Sultana, braving rocket and artillery attacks as they marched towards Gaddafi's hometown.
Shouting "Allahu Akbar" (God is greatest) and "Hold your heads high, you are Libyans," the fighters drove into Sultana -- the site of steady fighting in the past two days -- pushing Kadhafi's diehards back towards Sirte.
"They want a war, they are getting one. We will kick their butts," said one of the fighters, Saleh Drisi, as he jumped from his pick-up truck and barged into a house, searching for Kadhafi loyalists.
The column of fighters advancing on Sirte from the west were to join other NTC forces already at the gates of the city who have been fighting Kadhafi loyalists there since the weekend.
Nine of them were wounded, according to medics in Misrata hospital.
Fighting had also raged on Monday in Bani Walid when NTC fighters attacked the oasis town southeast of Tripoli where Gaddafi's son Seif al-Islam is believed holed up, possibly with his father.
Tuesday's talks in New York will "confirm the start of a new phase which began with the Paris summit and the beginning of an increased role in the United Nations," said French Foreign Minister Alain Juppe.
"The new Libya will symbolically be fully integrated into the United Nations," Juppe said, as the green, red and black flag of the victorious rebels was raised Monday for the first time at the UN.
Created on March 29 in London, the International Contact Group on Libya gathers 30 countries and several international organisations, including the United Nations, Nato and the Arab League.
It has worked to support the revolt against Gaddafi who ruled Libya for four decades, including unblocking the fallen regime's funds which had been frozen by governments around the world.
In Benghazi, the spokesman for the pro-NTC forces fighting in and around Sabha launched an urgent appeal for international aid on behalf of the region's residents.
Wardugu appealed to "France, Britain, the United States, to all Western nations, to the Arab countries and to humanitarian organisations to bring in aid," as people were suffering from a lack of food, water, electricity and medicine.
"Women, children, the elderly are dying every day. Some of the injured are transported to Benghazi (2,500 kilometres away) to receive treatment," he said.
The World Food Programme said meanwhile it has delivered one month of food supplies for 10,000 people who have fled fighting in Bani Walid.
"The delivery includes pasta, rice, pulses, vegetable oil and tomato paste and is enough to feed 10,000 people for one month," the UN agency said.