* Syria opposition hopes unity display to win West's backing
* Opposition says more arms is only way to topple Assad
* Opposition hope Obama victory will revive U.S. interest
By Rania El Gamal and Regan Doherty
DOHA, Nov 7 A plan to unite Syria's opposition groups has run into trouble almost as soon as it was put on the table, according to participants at talks intended to win support from foreign powers hoping to see Syrian President Bashar al-Assad toppled.
Western and Gulf Arab countries have backed the talks in Doha aimed at forging an anti-Assad coalition from rebel groups inside Syria and politicians in exile, principally the disparate factions of the Syrian National Council (SNC).
But in heated discussions in the Qatari capital on Tuesday night, SNC members harangued Riyadh Seif - the prominent SNC member who drew up the initiative - with some accusing him of pushing a U.S. agenda to sideline the Islamist-dominated SNC.
"Seif was not at all convincing yesterday. He told the council he was going ahead with the initiative with or without them," one SNC source said.
Opposition sources said many thought Seif's offer of 24 out of 60 seats would leave the SNC underrepresented in a proposed rebel assembly, which would later choose an interim government and coordinate with armed rebels to usher in a post-Assad era.
But the sources also said the Islamist Muslim Brotherhood, the most influential group within the SNC, had signalled its support.
"There are tensions and fears inside the SNC that they will cease to be relevant if they agree to the initiative. They want guarantees," one SNC source said. "But the Council are pragmatic. They are negotiating."
Countries including Turkey, Qatar and Saudi Arabia who have helped to arm rebels, as well as the United States and other Western powers, have lost patience with the fractious SNC and told it to make room for what U.S. Secretary of State Hillary Clinton called those "in the front lines fighting and dying".
Seif, hoping to secure official recognition and military support, wants his Syrian National Initiative to formally bring together politicians in exile with representatives of local groups and rebel forces operating inside Syria.
His proposal is the first concerted attempt to merge opposition forces to help end a 19-month-old conflict that has killed over 32,000 people, devastated swathes of Syria, and threatens to widen into a regional sectarian conflagration.
The Initiative would also create a Supreme Military Council, a Judicial Committee and a transitional government-in-waiting of technocrats - along the lines of Libya's Transitional National Council, which managed to galvanise international support for its successful battle to topple Muammar Gaddafi.
But Seif will have an uphill struggle to secure endorsement at Thursday's formal meeting.
The SNC is riven by differences between Islamists and secularists, between veteran exiles and those who lived for years inside Assad's police state, and between representatives of different Syrian regions.
One SNC source said the grouping had only agreed to the Doha conference under pressure from Qatar, Saudi Arabia, Turkey, the United States and France.
"It's being asked to reduce itself in size, which means not take a leading role as the political opposition inside Syria," said Salman Shaikh, director of the Brookings Doha Center.
"And it's being asked to do that with no real guarantees that more support will be forthcoming."
FEAR OF VACUUM
Western states have been reluctant to offer overt support to anti-Assad rebels, fearing that a divided and ineffectual opposition would open the door to rule by hardline Islamists.
Muslim Brotherhood domination has also deterred some Western countries from backing the SNC, though Washington has managed to work with Islamists who have risen to the top in post-revolution Egypt, Tunisia and elsewhere in the Arab world.
Opposition figures in Doha played down the role of hardline Islamists, or Salafis, including former al Qaeda fighters in Iraq and other jihadis from abroad for whom Syria is the latest cause celebre. They are accused of beheading soldiers and others seen as pro-Assad and committing other abuses.
"The issue is not the Salafis, the problem is Bashar al- Assad. If we have the capacity to support the (rebel) Free Syrian Army, the extremist element will diminish," said former SNC president Burhan Ghalioun.
"We need arms and until now we haven't had what we need. We need new arms, anti-aircraft arms. From the international community, we've seen many promises. But we wait and see."
Analysts say even if a new body is formed, its chances of winning over rebels on the ground are slim.
"It's difficult to see how rebels doing the fighting would be happy taking orders from Syrians sitting in five-star hotels," said a security analyst in Doha who did not want to be named.
General Mohammad al-Haj Ali, the highest ranking military defector, said Syria's economic collapse and continuing defections could bring down Assad within six months, whether the opposition unite and the West gives more arms or not.
"The state has collapsed economically and fighting is very expensive. The regime started to lose control over large swathes of land," he said.