SANAA As Yemenis prepare to vote in a poll many hope will give them a new start, a rift in the armed forces between outgoing President Ali Abdullah Saleh's relatives and a defected army general threatens to spoil political transition and tip Yemen into war.
On Tuesday 67 year-old Saleh, who has ruled the country for three decades, is to give way to his deputy, Abd-Rabbu Mansour Hadi, the sole candidate in Yemen's presidential vote, becoming the fourth leader forced from power since mass uprisings swept the Arab world last year.
The interim government formed in November when Saleh accepted a deal cut by his rich neighbors to avert civil war by easing him from power was to have separated his forces from those of his foes, after battles that left parts of the capital in ruins.
But Sanaa remains a city divided: armed tribesmen and defected military units control entire neighborhoods, ceding no ground and citing the prospect of Saleh hanging on to power behind the scenes as the justification for their presence.
Opposition leaders, keen to push on with the political transition, say the military standoff is itself temporary, and will resolve itself as Saleh's grip on the country ends.
"In November we were on the brink of civil war," said Mohammed Abulahoum, a former official in Saleh's party who quit to form his own. "Now we have a political settlement that should close the door on Saleh and his family for ever."
SALEH'S RELATIVES BOLSTERED BY U.S. TIES
Others are less convinced.
The transition deal, backed by the United States, gave Saleh immunity from prosecution over the killing of hundreds of protesters, and leaves his son and nephews in positions of power in the military and security forces.
If these members of his inner circle are allowed to stay, Saleh, who has vowed to return to Yemen as head of his political party, will be able to continue wielding influence from behind the scenes, protesters and activists say.
"Saleh might not rule the country but he could still play kingmaker," said Abdullah Al-Faqih, a professor of political science at Sanaa University. "He still has his ruling party, a son commanding the armed forces and allies holding the key ministries, he remains a political force to be reckoned with."
The interim government has vowed to restructure the armed forces, a task analysts say runs up against the vested interests of all of Yemen's warlords.
The fate of Saleh's relatives is clouded by their centrality in U.S. "counter-terrorism" strategy, aimed at an ambitious al Qaeda offshoot that has plotted attacks abroad, and capitalized on the turmoil over Saleh's fate to expand its foothold.
Saleh's immediate family has played a leading role in the fight against al Qaeda in Yemen, especially his nephew Yehya, who heads the country's highly trained counterterrorism unit.
That relationship may make Washington reluctant to see complete turnover among its closest military partners in Yemen, and could strengthen Saleh and his cohorts' hand domestically if they try to retain power, analysts say.
"In the coming months, the U.S. is going to be forced to re-evaluate how it is pursuing its war," said Yemen scholar Gregory Johnsen of Princeton University.
Opposing Saleh's relatives on the ground are troops following a dissident general and gunmen loyal to tribal leaders who turned on Saleh as protests against him gained momentum.
In the north, grubby-faced infants clamber on sandbagged checkpoints set up by rebel soldiers who careen through the city in armored trucks with Kalashnikov rifles and tubular rocket-launchers swinging on their shoulders.
Blackened, bullet-pocked ministerial offices with blown-out windows remain under the watchful eye of tribal fighters whose street battles with government forces last year razed an entire neighborhood to the ground.
"As long as these armed groups are out on the streets there remains the potential for a sudden outbreak of violence," Jamal Benomar, the United Nations envoy to Yemen told Reuters.
The dissident soldiers are loyal to Major General Ali Mohsen Al-Ahmar, Saleh's longtime confidant and partner in campaigns including a 2004-2010 war against rebels in northern Yemen that rights groups say witnessed multiple war crimes.
Ahmar, believed now to be in his late 60s, threw his weight behind the anti-government protest movement in March 2011, taking the First Armoured Division with him. His troops have subsequently fought Saleh's in the capital and elsewhere.
The schism has raised fears Yemen's army will not be ready to confront an increasingly dynamic al Qaeda offshoot, which has already gained a foothold in the country's rural south.
U.S. and Yemeni officials worry that any further loss of government control in the south could expand the group's influence near oil shipping routes through the Red Sea, and pave the way for future attacks on U.S. and Saudi targets.
The U.S. campaign against al Qaeda has included drone and missile strikes - including one against a U.S. citizen who Washington claims plotted the failed bombing of an airliner - which have killed civilians and fed anti-American sentiment.
It also includes logistical assistance and intelligence sharing with the several factions of the Yemeni military.
Mohsen's division has vowed to continue assisting the U.S. campaign but say tactics must change.
"We will support America and our allies in the West in the fight against radicalism, but it (America) must alter her strategy to prevent the loss of civilian lives," said Brigadier General Mohammed al-Sawmli, whose Brigade 25, was pinned down for months by Islamic militants last summer after Yemeni security forces quit southern Abyan province.
"The more civilians the U.S. kills the easier it is for al-Qaeda to recruit."
The ability of Yemen's military to continue that campaign is in doubt after a rebellion by Yemeni air force officers demanding the departure of their commander, a half-brother of Saleh's whom they accuse of bad management and corruption.
"The regime can no longer rely on the air force as a tool of repression against its own people," said Abdulghani Awdal, the air force general leading the efforts to oust the president's brother.
"If orders are given to carry out further air strikes on anti-government movements they will be refused. Half of the air force is out of the government's hands now."
(Writing by Tom Finn)