For 41 years Muammar Qadhafi has ruled Libya with only one real governing partner or potential counterweight: a council of Libya's powerful tribes.

With his government teetering, those tribes may now play a decisive role in deciding whether it survives or, under a set of demands circulated by the rebels challenging Mr. Qadhafi, gives way to an interim government.

Experts say longstanding tribal allegiances and animosities contributed to the revolt from the very beginning. The eastern region where the uprising began, known as Cyrenaica, is the heartland of the Senussi tribe, which produced King Idris I, the monarch who ruled Libya after it emerged from Italian colonial rule and achieved full independence in 1951.

It was Mr. Qadhafi's tribe, the Qadhadfa, which hails from western Libya, and two others, the Maghraha and the Warfalla, that overthrew the king in 1969. Easterners say that Mr. Qadhafi has starved their region of money and equipment ever since, aggravating the resentments left after the ouster of the Senussi king and leaving it in a more or less constant state of rebellion.

The Warfalla tribe is now wavering, with its leaders supporting the opposition but its lower ranks split. The two other tribes “still seem loyal so far to the regime, in which they have vested interests,” said George Joffe, a scholar of North Africa at Cambridge.

Other tribes in the western regions of Fezzan and Tripolitania are “watching and waiting,” Mr. Joffe said.

Another source of potential opposition might be the old Free Officers Movement, he added, an Arab nationalist group that carried out the 1969 coup but was subsequently marginalised by the Qadhafi government.

The Army, too, is a threat to the government.

“It's quite clear that the army, some 45,000 strong, has split, but in exactly what proportions we don't know,” Mr. Joffe said.

Mr. Qadhafi always mistrusted the Army and monitored its behaviour carefully. He paid particular attention to the units in the rebellious east, depriving them of the best equipment and training, which went to the more loyal tribes and paramilitary units, said Shashank Joshi, an associate fellow at the Royal United Services Institute in London, which specialises in the military.

Mr. Qadhafi himself hails from Surt, where his tribe remains strong. “The situation is more fluid than we imagine, with Qadhafi capable of launching military operations outside Tripoli,” including Air Force sorties, “and retaining his grip on Surt,” Mr. Joshi said. “Qadhafi has retained significant elements of the army and lost the elements he was always afraid he could lose, those affiliated with tribes he had targeted.”

The discovery of large deposits of oil changed the old bargaining among tribes and regions in Libya, something that both required and enabled Mr. Qadhafi to build a more centralised state to fully exploit the resource, said Jean-Yves Moisseron, Editor-in-Chief of the French-based magazine Maghreb-Machrek, which concentrates on the Arab world. Oil revenues also allowed Mr. Qadhafi to spread the wealth among tribes, reducing traditional conflicts, Mr. Moisseron said, and to build up a well-equipped paramilitary system loyal to his government.

In general, Mr. Joffe said, about 119,000 Libyans are part of the security services, including the Army of about 45,000, out of a largely desert country of about 6.4 million people.

In recent years, the oil-based pact in Libya has suffered from the global economic crisis of 2008, which reduced Libyan oil revenues by 40 per cent, Mr. Moisseron wrote in an article for Liberation, a French daily.

“The most worrisome sign for the immediate future of Col. Qadhafi is the rupturing of the tribal pact,” he wrote. But Mr. Joshi said Mr. Qadhafi retained significant strengths. He is thought to still control the Air Force, though some elements have defected. And while there have been clashes in Tripoli with sniper and small-arms fire in areas of the capital his soldiers, security forces and plainclothes officers are everywhere, the streets are quiet and many seem more fearful of Mr. Qadhafi than ready to celebrate his departure.

While the Colonel may often sound delusional when he speaks in public, he and his commanders have proved capable so far of using their forces with some care, Mr. Joshi said.

“There have been no large massacres, air power is being used in a calculated way and he is launching probing attacks,” while “making constant efforts in the suburbs of Tripoli to check small gestures of dissent.”

The struggle in Libya “could go on a long time,” he said. “Tripoli is not a bunker. And this is not the decision making of a man totally out of touch with reality.” — New York Times News Service

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