BENGHAZI, Libya (AFP) - Libya's rebels issued a Saturday ultimatum for Muamer Gaddafi's forces to surrender or face a military onslaught, as NATO said the strongman is still able to command his troops despite being on the run. National Transitional Council (NTC) chief Mustafa Abdel Jalil told reporters in the rebel stronghold Benghazi Tuesday that the respite was offered to mark the three-day Eid al-Fitr Muslim feast which follows the end of the Muslim fasting month of Ramadan. "This window of opportunity will be closed at the end of Eid al-Fitr (Friday in Libya)," Abdel Jalil said, adding that talks were under way with officials in towns including Gaddafi's birthplace Sirte to arrange their peaceful surrender. "From Saturday, if no peaceful solution is in sight on the ground, we will resort to military force," Abdel Jalil warned. He also warned that Gaddafi still enjoyed support inside Libya and outside the country. Gaddafi "is not finished yet," he warned, as NATO said the strongman is still able to command and control his remaining troops even though he is on the run. "He is displaying a capability to exercise some level of command and control," Colonel Roland Lavoie, military spokesman of the NATO air mission in Libya, told a news briefing in Brussels. "The pro-Gaddafi troops that we see are not in total disarray, they are retreating in an orderly fashion, conceding ground and going to the second best position that they could hold to continue their warfare," he added. Lavoie earlier told reporters that NATO's military mission in Libya was still necessary and would continue as long as Gaddafi's forces threatened civilians. "Despite the fall of the Gaddafi regime and the gradual return of security ... NATO's mission is not finished yet," Lavoie he said. Algeria meanwhile on Tuesday defended its decision to give shelter to Gaddafi's wife and three children, as the angry rebels demanded they be returned for trial. Algerian foreign ministry spokesman Amar Belani told AFP the decision to allow Gaddafi's wife Safiya, daughter Aisha and sons Mohammed and Hannibal to cross into the country on Monday was based solely on humanitarian concerns. "These people have been admitted to Algeria for strictly humanitarian reasons," Belani said, adding that UN chief Ban Ki-moon, the Security Council and number two leader of the rebels' NTC, Mahmud Jibril, had been informed. Just hours after crossing over, daughter Aisha gave birth to a girl, Algerian authorities announced Tuesday. The NTC, already at odds with Algiers for its refusal to recognise it as the legitimate authority in Libya, had reacted angrily when news broke Monday that some of their quarry had fled.