Rebels surged westward along Libya’s coast Sunday and Monday, seizing three more key towns and capitalizing on new momentum after more than a week of airstrikes by an international coalition.

News services described groups of opposition fighters lining up at gas stations along with residents, grabbing whatever fuel they could as the supply of petrol grew ever scarcer. The rebels were also taking stock of their supplies of food and weapons as they prepared to push toward Sirte, the home town of Libyan leader Moammar Gaddafi.

“We have a serious problem with petrol. This is a big problem,” Ahmed Abdinibi, a 19-year-old year old student turned volunteer fighter, told the Associated Press outside a gas station in Ras Lanuf.

“Maybe we have enough for just another day. . .Maybe we will not find another place like this.”

Hours earlier, the rebel capital of Benghazi had erupted in celebratory gun and rocket fire amid rumors that that Sirte, a Gaddafi stronghold, had fallen.

But those rumors seemed to be unfounded. Opposition spokesman Mustafa Gheriani said he did not have information that the rebels were in control in Sirte, and news services later reported that there was no fighting in the town, and no sign of rebel forces.

Instead, dozens of fighters loyal to Gaddafi could be seen roaming the streets of Sirte Sunday night, the Associated Press reported. Witnesses told AP that bombing was heard in the town Sunday night and again Monday morning.

Qatar, one of two Arab nations participating in the NATO-led airstrikes, announced Monday that it would recognize the Libyan National Transition Council as the “sole legitimate representative” of the Libyan people. The announcement, carried by the official Qatar News Agency, was posted on the Web site of the Qatar foreign ministry.

In Washington, U.S. officials were guardedly optimistic about the reversal of fortunes for the rebels. President Obama is scheduled to address the nation on Monday night, and officials said he will be able to show that the operation is starting to achieve its goals. Obama has faced mounting criticism from some lawmakers, who fear that the United States could get bogged down in a foreign intervention without a clear objective.

Senior U.S. officials said Sunday that Gaddafi’s 41-year rule could end with the implosion of his regime or a negotiated settlement rather than an outright rebel victory.

“One should not underestimate the possibility of the regime itself cracking,” Defense Secretary Robert M. Gates said Sunday on NBC’s “Meet the Press.

But analysts warned that, although the rebels have seized the initiative in eastern Libya, they still face formidable obstacles.

NATO members agreed Sunday evening that the alliance would assume control of the international military campaign against Libya. It had earlier taken over from the U.S. military in leading enforcement of an arms embargo and a no-fly zone and had debated for days whether to coordinate the politically riskier strikes on Libyan ground forces.

With Gaddafi’s air-defense equipment largely destroyed and NATO stepping up to assume command, the United States will be able to reduce its role, Gates said.

“Within the next week or so, we will begin to diminish the commitment of resources,” he said. He added, however, that the United States will stay on in a supporting role and acknowledged that it is unclear how long the operation will last. He and Secretary of State Hillary Rodham Clinton on Sunday defended the Libya campaign, saying it is helping avert a humanitarian catastrophe.

The coalition again targeted the Libyan capital, Tripoli, with witnesses reporting at least 10 loud explosions Sunday night, followed by bursts of antiaircraft fire.

As rebel forces headed toward Sirte, 278 miles east of Tripoli, reporters on a government trip to the city heard at least half a dozen explosions there and saw warplanes circling overhead.

Libyan state television reported what it said were the first coalition strikes against Sirte, but by late Sunday it had still not broadcast details of the loyalist army’s rapid retreat across more than 200 miles of coastal highway over the previous 24 hours.

Government spokesman Moussa Ibrahim said Sunday evening that although its forces had pulled back, “we are still very strong on the ground.” He said the airstrikes were “a plan to [put] the Libyan state in a weak negotiating position.”

The rebels’ recovery began Friday, when they recaptured the strategic town of Ajdabiya after coalition bombings weakened Gaddafi’s forces. The rebels then charged on to Brega and Ras Lanuf, sparsely populated petroleum centers, and took over the coastal town of Bin Jawwad. They had been repulsed at Bin Jawwad earlier in the month, as Gaddafi’s forces launched an aggressive counterattack.

“The big question now is, can they really go beyond where they were three weeks ago?” said Dirk Vandewalle, a Libya specialist at Dartmouth College, referring to the rebels.

The coalition has focused its attacks on Libyan soldiers, tanks and weaponry outside the cities. But it has hesitated to strike inside urban areas for fear of killing civilians. Gaddafi, however, has soldiers and armored vehicles inside cities such as Misurata, a rebel outpost in western Libya where fighting continued Sunday.

The latest rebel victory in eastern Libya “doesn’t necessarily mean that Gaddafi’s days are numbered,” said Andrew F. Krepinevich, director of the Center for Strategic and Budgetary Assessments.

As the rebels push toward Sirte and, potentially, Tripoli, the allied forces could be faced with another dilemma. Their mandate from the U.N. Security Council is to protect civilians who face the threat of bombardment.

But what if the rebels are attacking, and the pro-government forces are defending turf?

“It’s been very clear up to this point that it is the regime of Colonel Gaddafi that is engaged in horrendous acts against civilians, and, therefore, it is those forces being targeted,” said a senior U.S. official, who briefed reporters on the condition of anonymity.

He did not directly answer when asked whether coalition forces would back a rebel offensive on Tripoli or Sirte. But he said the operation is aimed at protecting noncombatants, not helping the rebels.

Obama has called for Gaddafi to relinquish power. But Gates said Sunday that the conflict “eventually is going to have to be settled by the Libyans themselves. Perhaps the U.N. can mediate. . . . But in terms of commitment, the president has put some very strict limitations in terms of what we are prepared to do.”

Clinton said a U.N. envoy, former Jordanian foreign minister Abdul-Illah Khatib, will travel to Tripoli to carry “a very clear message to Gaddafi.”

She said on “Meet the Press”: “We’re also sending a message to people around him: Do you really want to be a pariah? Do you really want to end up in the International Criminal Court? Now is your time to get out of this.”

Bahrampour reported from Benghazi and Sheridan reported from Washington. Staff writer Greg Jaffe in Washington contributed to this report.