BENGHAZI, Libya — Forces loyal to Libyan dictator Moammar Gadhafi advanced further eastward Sunday, moving into the coastal city of Brega and putting new pressure on the United States and its allies to either intervene militarily or risk seeing the anti-Gadhafi movement collapse.
For rebels battling Gadhafi in the nearly month-old uprising, if they cannot retake Brega, it will be the fourth city they have lost in three days, a dramatic reversal of fortunes since they swept out of eastern Libya last month and seemed days away from the outskirts of the capital, Tripoli. Three of the four cities _ Zawiya, Brega and Ras Lanuf _ have refineries.
While discussions of an international no-fly zone have intensified since the Arab League's endorsement of one Saturday, it remains unclear whether such a step could now halt Gadhafi's overwhelming firepower — or, even if it could, whether it will come in time.
On Sunday, rebel fighters said they moved to the outskirts of Brega after coming under attack from missile strikes from ships at port as well as strikes from the air.
The battlefield developments appeared to set up a looming confrontation between rebels and pro-Gadhafi forces in the city of Ajdabiya, a major gateway to the rebel capital of Benghazi, Libya's second-largest city.
Control of Ajdabiya would give Gadhafi sway over a major crossing point, and, in theory, the prospect of surrounding Benghazi by moving some of his forces directly to Tobruk in far northeastern Libya.
President Barack Obama has demanded that Gadhafi leave power, but he has so far employed little leverage to accomplish that goal.
The 22-member Arab League, normally hostile to any outside intervention in its region's internal affairs, on Saturday took the unprecedented step of asking the U.N. Security Council to impose a no-fly zone over Libya to prevent Gadhafi from using military aircraft.
The United States and other Western nations wanted that endorsement as political cover, but imposition of a no-fly zone seems days away at best. And it would not stop Gadhafi from using his ground forces to attack the rebels.
In Washington, a senior Obama administration official described the Arab League decision as "an important step," but added that there "are still other hurdles to overcome." The official requested anonymity in order to speak freely on a topic he wasn't authorized to address publicly.
The official indicated that one open question remained whether Arab powers would actually take part in imposing a no-fly zone, a condition the Obama administration has said it wants in order to avoid the perception that the move represented unilateral U.S. intervention into a region where anti-U.S. sentiment is high.
"As we've said, we want to see both regional endorsement and regional participation," explained the official.
Obama's national security adviser, Thomas Donilon, told reporters Thursday that the White House wants more than just rhetorical support from Libya's neighbors.
"We're going to be seeking actual support by those nations — the Arab League, the (Saudi-led Gulf Cooperation Council) and the African nations — to participate in any of these efforts as they go forward," Donilon said. "Again, not just rhetorical support, but actual participation."
Secretary of State Hillary Clinton is due to discuss Libya with her counterparts at a meeting Monday of foreign ministers from the G-8 group of nations in Paris.
Sen. Charles Schumer, D-N.Y., said Sunday that the Arab League's decision "makes a no-fly zone more likely." He spoke on NBC's "Meet the Press."
In lieu of a no-fly zone, which rebel fighters are keenly aware the United States is hesitant to enforce, the Gadhafi opposition forces said they want the West to provide more advanced weapons than those they have taken from looted military bases. Yet many rebels do not know how to use the weapons they have now.
The state of fighting in and around Brega was murky Sunday. Cell phone access there and in nearby Ajdabiya appeared to be limited, if any, cutting off the rebels' main means of communication.
On Friday, Gadhafi's regime took Western reporters to tour Zawiya, 30 miles west of Tripoli, which Gadhafi's forces recaptured after days of bloody siege, another major setback to the rebels.
(Youssef reported from Libya, Strobel from Washington. Jonathan S. Landay contributed.)
MORE FROM MCCLATCHY
Despite reluctance, U.S. could be forced to act in Libya
Who'll control Libya's oil economy if Gadhafi falls?
Like new Middle East, Obama doctrine is a work in progress
Wave of protests now touches nearly all of Arab world
Follow McClatchy on Twitter.