DOHA - 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 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 US agenda to sideline the Islamist-dominated SNC.

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.

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 US Secretary of State Hillary Clinton called those "in the front lines fighting and dying."

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