AMMAN/LONDON (Reuters) - Syrian President Bashar al-Assad looks increasingly cornered, his authority seriously wounded by rebel raids at the gates of Damascus and his ability to wield superior firepower complicated by political constraints.
On paper, the military balance remains in Assad's favor, with army defections still relatively small. Rebel strength, estimated variously at 20,000 to 30,000, is less than a tenth of the army's. External armed intervention in favor of the opposition is unlikely and the security services, manned mainly by members of his minority Alawite sect, remain intact.
But while Free Syrian Army (FSA) insurgents seeking an end to 42 years of Assad family rule are unable to hold territory, and a purely military victory seems out of reach, their multiplying raids appear to be achieving a political momentum that cannot be slowed simply by Assad's bigger armed clout.
And Assad's capacity to deploy his army's full might to end an 11-month-old uprising is limited by fears it might backfire by simply spurring more defections.
Yezid Sayigh, Senior Associate at the Carnegie Endowment's Middle East Center, wrote there was no longer any serious doubt that "the government's days are numbered" but it was an open question how long it could hang on.
"The regime cannot win, but it certainly can resist and prolong the conflict," he wrote in a commentary.
Armed clashes, now increasingly punctuating what began as a non-violent protest movement, have raised fears of a full-scale conflict in Syria, a Sunni Muslim-majority country of 23 million which also has Alawite, Druze, Christian and Kurdish minorities.
The United Nations says more than 5,000 people have been killed in Assad's crackdown on protests. Syria says foreign-backed "terrorists" have killed 2,000 soldiers and police.
In responding to the spreading insurgency, Assad's military options amount to a dilemma: If he calls out the vast majority of his conscript forces, they may turn against him when ordered to fight in the communities from which they come. And if his core, mainly-Alawite forces resort to increasing levels of violence, they may push more people into the opposition camp.
The result, some analysts say, may be a gradual escalation of violence that sees Assad rely increasingly on Alawite support, with the attendant risk of greater sectarian conflict.
"The more Assad is cornered the more brutal he is becoming. His advisers are telling him they are winning. They are delusional," a Western diplomat based in the region said
The rebels' temporary seizure of some Damascus suburbs on Jan 26-29, and a January 27 attack on anti-Assad demonstrators in the second city Aleppo, scene of an expanding protest movement, are likely to have unnerved the ruling elite.
While Assad has retained strong support from allies Russia, Iran and the powerful Shi'ite Lebanese group Hezbollah, he is under unprecedented Arab and Western pressure to step down.
The exact strength of the dissident soldiers is not known and Syria's ban on most foreign media makes it hard to verify events on the ground.
But analysts say increased defections among the military are forcing Assad to rely more heavily on two main units composed mainly of troops from his minority Alawite sect, the Republican Guards and the Fourth Armoured Division.
These units are using heavier force, such as shelling from tanks and fixed artillery, to put down the uprising, diplomats and opposition sources said, prompting more desertions and popular support for the insurgents.
Shashank Joshi of the Royal United Services Institute military think tank in London said the government "is only going to face increasing numbers of fronts on which to fight."
"The opposition will also grow increasingly willing and able to go on the offensive. The more troops it deploys, and the more forces it uses, the greater the rate of defections," he said.
Sayigh told Reuters he assumed rebel activity would result in "attrition. The regime's assets will slowly wear down."
"There presumably will come a time when the regime loses the ability to besiege or retake towns and neighborhoods. Once that becomes evident then I guess there will be a tipping point. But I just don't see that happening yet."
Sayigh said up to three quarters of the army was believed still in its barracks because the government did not want "large numbers of conscripts and ground forces face to face with their own people in towns and cities they may come from themselves and tell them to shoot people, perhaps even their own family."
"This is the sure recipe for the army to fall apart. We saw this in Iran in 1978 and 1979 for instance. The regime definitely doesn't want to risk that."
The Damascus suburbs that fell under the control of FSA fighters last week were subsequently retaken by the army. But with overstretched core forces in the midst of hostile urban areas, and outgunned rebels avoiding open, prolonged battles, analysts say the military's grip on the suburbs may weaken again, as rebels regroup and mount guerrilla attacks, forcing loyalist troops, to withdraw or thin their presence.
A similar scenario took hold in several towns and cities that were stormed by the military, such as the towns of Rankous in mountains north of Damascus, Rastan near the city of Homs and the cities of Idlib, Khan Sheikhoun and Homs.
"The more Assad pushes regular troops into battle the more he faces bigger defections," said Fawaz Tello, a senior Syrian activist who fled to Cairo in the last few days.
A European official following the situation on the ground said Assad had tried to placate Sunnis in the army by promoting many Sunnis to the rank of general and other high level ranks in the latest annual military appointments list issued last month.
He added that core units, mainly the Republican Guards and the Fourth Division, were being increasingly used beyond their main mission of securing the capital.
General Mustafa Ahmad al-Sheikh, the highest ranking member of Assad's military to defect, said Assad could only rely now on one-third of the army to fight for him, with tens of thousands of soldiers having either defected and gone home or joined the rebels.
In a January 24 commentary the International Crisis Group's Peter Harling wrote the army was "fragmenting, slowly but surely ... The regime's territorial control depended on the protest movement remaining largely peaceful. Now that an insurgency is spreading, it is losing its grip."
Reporting by William Maclean; Editing by Samia Nakhoul