BEIRUT (Reuters) - Yemeni President Ali Abdullah Saleh's 32-year rule seems near collapse. His exit would spell uncertainty for his broken country and discomfiture for U.S. and Saudi friends, still backing their "ally" against al Qaeda.
The killing of more than 50 protesters in Sanaa on Sunday has turned a trickle of defections into a torrent as Yemeni diplomats, military officers, tribal leaders and politicians hasten to declare support for the anti-Saleh opposition.
"Saleh is finished," said Philip McCrum, an independent analyst. "He is only clinging on because the Saudis and Americans are loathe, even at this late hour, to give him up."
But the 68-year-old leader has no obvious successor, there is no clear mechanism for a peaceful transition, and his tribal and military foes may fight over the spoils of a post-Saleh Yemen.
In the latest of a series of political concessions, Saleh offered on Tuesday to step down after parliamentary elections in January 2012. A spokesman for an opposition coalition rejected the idea, saying "the coming hours will be decisive."
Yet instead of victory for a pro-democracy movement inspired by the overthrow of autocratic presidents in Egypt and Tunisia, fragile Yemen could fall apart as a nation-state.
"It is not unthinkable that the borders between north and south Yemen will reappear, or that other lines between local fiefdoms will appear and that you'll have many civil wars in different parts of the country," said Volker Perthes, director of the German Institute for International Politics and Security.
Almost any change in Yemen would alarm neighboring Saudi Arabia, which feels directly threatened by al Qaeda militants based there. It would also frown on any transition to democracy in Yemen -- viewing it as a disturbing departure from the one-man rule practiced across its Arabian peninsula backyard.
McCrum said Washington and Riyadh considered Saleh useful in their fight against the Yemen-based al Qaeda in the Arabian Peninsula (AQAP) and propped him up for fear of the unknown.
"Both countries view Yemen from a purely self-interested, security perspective and from that point of view, Saleh's departure makes them nervous," he added.
AL QAEDA SIDELINED
Ambitious al Qaeda militants have found refuge in the mountains and deserts of Yemen, whose extreme poverty makes for a fertile recruiting ground; but their popularity is debatable.
"AQAP has been pretty much sidelined in the current unrest, indicating that its ideology is still very marginal in Yemeni society," said McCrum, arguing this was unlikely to change soon.
"So, with the 'near enemy' (Saleh) now gone, the AQAP core membership will likely focus its attentions on the 'far enemy' (the United States) instead. The ongoing tension and violence will give it the breathing space to do so," McCrum added.
In the past two years AQAP has tried to kill Saudi Arabia's security chief and to bomb U.S. targets, including airliners.
Chaos in Yemen, an impoverished land of 23 million people with plenty of guns, could affect its oil-rich Gulf neighbors as well as vital shipping lanes in the Red Sea and Gulf of Aden.
Saleh himself may still emulate Libyan leader Muammar Gaddafi's choice of violent resistance to a popular revolt, using military units still loyal to him, rather than go quietly like Egypt's Hosni Mubarak or Tunisia's Zine al-Abidine Ben Ali.
He played on these themes on Tuesday, telling his military commanders: "Those who want to climb up to power through coups should know that this is out of the question. The homeland will not be stable, there will be a civil war, a bloody war."
Saleh's remarks followed the defection on Monday of his kinsman and key military commander, General Ali Mohsen -- a man who in the past eased the return of Yemeni jihadists from Afghanistan and who often liaised with militant groups.
"His defection definitively tips the balance of power away from Saleh," wrote Yemen researcher James King.
"Yet Mohsen is widely considered a brutal military leader and he has come to symbolize the dominance of one small tribe, the Sanhan, over the country. As a result, many Yemenis fear that his motives may be more sinister than democratic change."
In a separate speech to tribal leaders in Sanaa, Saleh also raised the specter of a carve-up of Yemen between northern Shi'ite rebels, southern secessionists and al Qaeda militants.
Yassin Noman, rotating head of Yemen's opposition coalition, said he did not believe that defecting tribal and military leaders would turn their weapons on Saleh. But he feared a bloody conflict if the president hung onto power Gaddafi-style.
"It will cost a lot. It will not be restricted to the army only. I think it will go over all the country, even the tribes."
Washington, which had urged opposition groups to accept Saleh's dialogue offers, now advocates "peaceful transition."
King said the United States, which gave Yemen $175 million mostly in security aid last year, risked being seen as "one of a crumbling few pillars that prop up an enfeebled regime."
By pressing Saleh to quit, it could still undercut an al Qaeda portrayal of a Yemen besieged by "an unholy alliance between a corrupt, repressive government and its American master."
(Additional reporting by Cynthia Johnston and Mohammed Ghobari in Sanaa; editing by Ralph Boulton)