* Opposition quarrelling ahead of vital talks
* Assad profiting from opposition disunity
* Dissidents criticise Muslim Brotherhood role
LONDON, March 28 (Reuters) - Far from the bloodied streets of Syria and the dungeons of Bashar al-Assad, the largely émigré opposition that aspires to replace him is still squabbling ahead of what could be a make-or-break meeting of a coalition of countries intent on regime change, but equally at a loss about how to achieve it.
While the Assad government appears emboldened after its offensives against outgunned rebels in Homs, Idlib and the capital Damascus, the fragmented opposition, meeting in Istanbul ahead of the "Friends of Syria" meeting on April 1, seems still unable to cohere behind a unifying national project.
Some dissidents among the rebels are also denouncing the Syrian National Council (SNC) - the umbrella group recognised by leading Arab and Western nations as a "legitimate interlocutor" - as a front for the Islamist Muslim Brotherhood bankrolled by Gulf states such as Qatar.
Kamal al-Labwani, a physician and prominent opposition leader who resigned from the SNC this month, called it "an opposition under the cloak of fanatics hiding behind a veneer of stupid liberals".
According to Labwani, the ostensibly secular and multi-party SNC is no more than a façade for the Muslim Brotherhood, a claim that chimes with Assad's contention that the year-long uprising is an Islamist plot that will deprive Syria's minority sects of their freedom.
The Assad rule is built around the Alawite sect, a heterodox offshoot of Shi'ite Islam, but uses this narrative to persuade fearful minorities such as the Christians that their future is in jeopardy if the Sunni majority, around three quarters of the population, comes to power.
"The Brotherhood are the dominant force in the Council," Labwani said. "There is the Hama faction, the Damascus faction and the Aleppo faction of the Brotherhood, the Hama faction is backed and funded by Qatar and Turkey."
As the rebellion has increasingly resorted to arms in the face of relentless repression by Assad's forces, "they are setting conditions for who they arm. And those who are not Islamists or religious, they are not being supplied with guns", he said.
The Brotherhood has been the big winner in the upheavals of the Arab Spring, winning elections in Tunisia and Egypt after the revolutions that toppled their dictatorships last year, and advancing in other Arab countries from Morocco to Libya.
The Syrian branch of the Brotherhood this week published a "national covenant", promising a civil constitution embodying equal rights for all religious minorities and for women.
"We don't have an agenda to exclude others or to monopolise", Melhem al-Droubi of the Syrian Brotherhood told Reuters. "There may be differences but the aim of everybody is to bring down the regime of Bashar al-Assad."
It is not just the role of the Brotherhood that is coming under fire.
Haitham al-Maleh, a veteran opposition figure and human rights lawyer who was jailed by both Assad and his father, bitterly denounces the autocratic habits of Burhan Ghalioun, the liberal Sorbonne professor who is the figurehead of the Council.
"I want to see the council act democratically. Until now, they are acting like the (ruling) Baath Party," Maleh, who withdrew from the SNC along with Labwani, told Reuters.
"Ghalioun wrote his last speech in Istanbul and did not show it to us. They went to meet Kofi Annan [the former UN secretary general now acting as special envoy for Syria] in Ankara and did not inform us. This is a disaster. I cannot be in a place where I am treated as a nonentity", Maleh said. "There is a monopoly in the leadership and no transparency".
U.S. Secretary of State Hillary Clinton called on the Syrian opposition on Tuesday to commit itself to include, and protect the rights of, all Syrians in a political transition.
French Foreign Minister Alain Juppe has also urged the opposition to stop quarrelling.
"There are some opponents whose attitudes are seriously weakening the opposition - as long as they continue to tear themselves apart and fight amongst themselves," Juppe said in an interview with French newspaper Le Monde.
"We are doing everything to try to unite the opposition around the Syrian National Council and to convince them to be more inclusive, to welcome Alawites, Christians," he said. "They are not doing well enough.
Amid this jostling, most Western and Arab nations fear the bloody stalemate in Syria is opening up space for jihadis such as al-Qaeda, sidelined by the last 15 months of Arab revolution but now presented with an opportunity to re-enter the fray.
U.S. intelligence officials have linked al-Qaeda to recent bombings against regime targets in Damascus and Aleppo.
"The main worry in the west is the infiltration of Islamist jihadis, including possibly al-Qaeda coming over the border from Iraq", said Syrian expert Patrick Seale, biographer of Bashar's father, the late President Hafez al-Assad. "The people carrying out these suicide attacks ... are almost certainly al-Qaeda", he said.
"The United States, Britain and France are having doubts about the opposition because they don't want to be allied with al-Qaeda," Seale said.
Ultimately, Seale argues, even though the Assad regime is under siege it is in a better position than it should be because the opposition is in such disarray, and the West and most Arab countries are reluctant to help it with arms.
"The Brotherhood have penetrated the SNC and the Free Syrian Army" made up largely of army defectors, he said. "They have taken Islam as their rallying cry and that is why the minorities are frightened."
While the opposition may have fatally destabilised the Assad government, it seems unable to overthrow it.
"The economy is collapsing. The image of Bashar has been destroyed. He is seen as a brutal dictator and his legitimacy has gone down the drain", said Seale. But he added: "In the opposition it is chaotic and they are squabbling. The problem is everyone wants to be Number One".