RAS LANOUF, Libya — Repeated airstrikes by Libyan warplanes on Monday illustrated the edge Moammar Gadhafi holds in his fight against rebel forces marching toward the capital: He controls the air. After pleading from the uprising’s leaders, Britain and France began drafting a U.N. resolution for a no-fly zone in Libya that could balance the scales.

President Obama warned that the U.S. and its NATO allies are still considering military options to stop what he called “unacceptable” violence by Gadhafi’s regime. NATO decided to boost flights of AWACs surveillance planes over Libya from 10 to 24 hours a day, the U.S. Ambassador to NATO Ivo Daalder said.

Libyan warplanes launched multiple airstrikes Monday on opposition fighters regrouping at the oil port of Ras Lanouf on the Mediterranean coast a day after they were driven back by a heavy government counteroffensive aimed at stopping the rebel drive toward Tripoli, Gadhafi’s stronghold.

One strike hit near a gas station in Ras Lanouf, blasting two large craters in the road and wounding at least two people.

The rebels oppose any Western ground troops deploying in Libya, but they’re pressing for a no-fly zone to relieve them of the threat from the air. The rebels can take on “the rockets and the tanks, but not Gadhafi’s air force,” said Ali Suleiman, a rebel fighter at Ras Lanouf. “We don’t want a foreign military intervention (on the ground), but we do want a no-fly zone. We are all waiting for one.”

Arab Gulf countries joined the calls for a no-fly zone, with the foreign minister of the United Arab Emirates saying a conference of his country’s neighbors that the U.N. Security Council should “shoulder its historical responsibility for protecting the Libyan people.”

Still, Western military intervention does not seem imminent — and the warnings may be an attempt to intimidate Gadhafi with words before deeds. British and French officials said the no-fly resolution was being drawn up as a contingency and it has not been decided whether to put it before the U.N. Security Council, where Russia holds veto power and has rejected such a move. Western officials have said a no-fly zone does not require a U.N. mandate, but they would prefer to have one.

In the battles over the weekend, Gahdafi’s forces unleashed their strongest use of airpower yet in the nearly three-week-old uprising. A powerful assault by warplanes, helicopter gunships and heavy barrages of artillery, rockets and tank fire drove the opposition forces out of the town of Bin Jawwad, 375 miles east of the capital.

The counteroffensive blunted what had been a steady advance by a force of 500 to 1,000 rebel fighters pushing down the coastal highway along the Mediterranean Sea west toward Tripoli. The rebels were forces back to Ras Lanouf, about 40 miles to the east.

The past three days of fighting killed 30 rebels and wounded 169, said Gebril Hewadi, a doctor at Al-Jalaa Hospital in Benghazi.

The rebels are now struggling to set up supply lines for weapons, ammunition and food, with many living off junk food, cookies and cans of tuna. They are waiting for rocket launchers, tanks and other heavy weapons to arrive with reinforcements from their headquarters in the eastern city of Benghazi.

The fighting also appears to have outright shut down oil operations at Ras Lanouf and the larger nearby oil port of Brega, which were already operating at minimal capacity. Ahmed Jerksi, an oil official at Brega, said that port had stopped working the past few days because all the personnel had fled. He and Mustafa Gheriani, an opposition spokesman in Benghazi, said they believed Ras Lanouf had stopped as well.

The fighting in Libya, which produces nearly 2 percent of the world’s oil and delivers most of it to Europe, continued to push oil prices ever higher. Traders are worried the strife may spread to other oil-rich nations.

Libya appears to be sliding toward a civil war that could drag out for weeks, or even months, as rebels try to oust Gadhafi after 41 years in power. The opposition already controls the entire eastern half of the country — from Ras Lanouf to the Egyptian border.

Libya’s main population centers lie along the country’s main east-west highway on the Mediterranean coast and rebels are trying to push the front line westward toward the capital. Their biggest obstacle along the way is Sirte, Gadhafi’s hometown and a bastion for his forces, just west of Bin Jawwad. Taking Sirte would be a major morale boost to the opposition and give it almost a clear way to Tripoli.

The opposition also holds several cities in the west close to Tripoli. But the government appeared to have taken back one of them, Zawiya, after days of heavy fighting. Monday saw the heaviest bombardment yet in the city, just 30 miles outside Tripoli, said one resident. He said tanks and artillery opened fire around 9 a.m. and by the afternoon, rebels had been driven out Zawiya’s main square.

“The tanks are everywhere,” said the resident, who fled the city in the afternoon. “The hospital is running out of supplies. There are injured everywhere who can’t find a place to go.”

Gadhafi’s warplanes give him an extra edge in the fight against rebels. At the very least, they intimidate rebels battling in open desert with little cover.

Still, so far Gadhafi has not brought — or not been able to bring — the full firepower of the air forces against the rebellion. In Sunday’s fighting, the massive artillery and rocket bombardment did more to break the rebel ranks.

That may be in part because of the weakness of his air arsenal and worries over the loyalty of its personnel. Over the decades, Gadhafi built a large air force, estimated at around 500 combat aircraft and helicopters. On Google Earth, dozens of Soviet-era MiG and Tupolev fighters can be seen lined up at air bases in Sirte and in the deserts of southwestern Libya.

But well over half of the aircraft are believed to be unable to fly, because they are outdated and because under decades of sanctions Libya was unable to procure spare parts, according to GlobalSecurity, a U.S.-based website.