The United Nations Security Council members -- United States, United Kingdom, France, Germany, and Lebanon -- are putting the final touches on their Libya no-fly zone resolution draft. The sponsors intend to introduce the draft to the full Security Council during Tuesday afternoon's session on Somalia.

The current draft is an amalgamation of the initial France-British draft and the Arab League's position. It would give political and legal authorization for the establishment of a no-fly zone. 

The text does not go into the specifics of who would be involved in the enforcement, but such details would be worked out by NATO and the Arab League. The Russians tell Fox News that they seek clarity on who would participate in a no-fly zone and how before signing onto the resolution. Western council diplomats say they anticipate tough negotiations with veto-wielding China.

The draft resolution also calls for more robust enforcement of an arms embargo and an end to mercenary involvement in the North African country.

The resolution talks comes as Libyan rebels lost control of their last town west of Tripoli on Tuesday and struggled to stall or outrun Muammar al-Qaddafi's forces as they raced eastward. With a punishing blockade, airstrikes and long-range missiles, Qaddafi's forces neared opposition strongholds, apparently hoping either for outright victory or to force residents to turn against the rebels.

With the victory in Zwara and the west largely consolidated under Qaddafi, government troops and warplane raced eastward, their all-out assault on the city of Ajdabiya easily outpacing French and British efforts to build support for a no-fly zone over Libya.

Opposition fighters were left with only one foothold in the country's west, where the Libyan leader's strength is greatest, and teetering control of some of the eastern cities that have been their support base, refuge and source of supplies.

Qaddafi's forces reached the Ajdabiya's outskirts on Tuesday afternoon, pounding the city entrance with long-range missiles, tank fire and airstrikes. One bomb destroyed a rebel camp, a panicked local activist told The Associated Press, and another wrecked a key rebel supply road.

"This isn't one or two planes. They are like a flock!" he said, as explosions went off in the background.

He said Qaddafi's forces had also pounded the crucial eastern road that linked the city to other rebel strongholds.

Residents were fleeing to nearby villages, he said.

Rebel spokesman Ahmed al-Zwei, among a group of fighters at Ajdabiya's western gate, said his comrades were hoping to try stall the government advance: "God willing, no, no, no, they will not reach Ajdabiya. God willing we can push them back." Later, with the sounds of gunfire behind him, he said missiles were coming in from the sea and bombs were coming from warplanes above.

"Just now they hit a group of fighters. They are dead, wounded," he said in a harried phone call interupted by shouting orders. He claimed Qaddafi's forces haden't yet entered the city.

Lt. Col. Mohammed Saber, who defected from the army to join the rebels, said young men were coming by the hundreds to protect the city, even though there were not enough guns to go around: "They don't have the arms, but they have the will to fight."

Libyan state television claimed the battle was already won. The report said Qaddafi's troops were "completely in control of Ajdabiya and are cleansing it from armed gangs."

French Foreign Minister Alain Juppe suggested in a radio interview that events in Libya have already outpaced diplomatic efforts.

"If we had used military force last week to neutralize some airstrips and the several dozen planes that they have, perhaps the reversal taking place to the detriment of the opposition wouldn't have happened," Juppe told Europe-1 radio. "But that's the past."

The victory in Zwara, a seaside town about 30 miles from the Tunisian border, reversed the early rebel gains in the uprising against his rule that began on Feb. 15. Government troops had surrounded the town of 45,000 on Monday and bombarded it with tanks and artillery for hours, killing at least four rebel fighters, several residents said.

Even as Zwara fell, the Obama administration on Monday held its first high-level talks with the Libyan opposition and introduced a liaison to deal full time with their ranks. It remained undecided about exactly how much support to lend a group it still knows little about while turmoil and uncertainty increase across the Arab world.

Government troops have also blockaded Misrata, Libya's third-largest city, 125 miles southeast of Tripoli.

"We are short on antibiotics and surgery supplies and disposable equipment," said a doctor in the city. "We feel so, so, isolated here. We are pleading with the international community to help us in this very difficult time."

The doctor said naval ships in the Mediterranean port were blocking aid ships. Another resident said townspeople were relying on poor quality home-dug wells normally used to water gardens. He said in many parts of town, the water network was cut, and tankers that traditionally supply rooftop tanks weren't able to enter Misrata.

Government troops have scored victories using overpowering bombardments with artillery, tanks, warplanes and warships. Such an assault drove rebel fighters out of the western city of Zawiya last week.

The rebel's main stronghold, Benghazi, remained firmly in their hands on Tuesday. A Tuareg lieutenant from Mali who has fought for the Libyan government since 1993 said the government wants to retake Benghazi, but doesn't want to attack the city itself. He says the government will try to convince the residents of Benghazi to force militants out.

"Everyone in Benghazi is still watching Libyan state television so the government will try to get its message across like this," he said, speaking on condition of anonymity to avoid reprisal. "The idea is to surround Benghazi but to leave one exit open for the rebels. If we can get the rebels to leave the city then we will move troops in between them and the city and fight them in the open desert."

Fox News' Jonathan Wachtel and the Associated Press contributed to this report.