Violence flared again on the Turkish border and the line separating Syria from the Golan Heights, highlighting how the conflict is spilling into the region.
Reformist Damascus cleric Mouaz Alkhatib flew to Cairo to seek the Arab League's blessing for the new assembly that unanimously elected him as its leader.
Mr Alkhatib, 50, jailed several times for criticising Mr Assad, fled into exile this year. He has long promoted a liberal Islam tolerant of Syria's Christian, Alawite and other minorities.
"The first step towards recognition will take place at the Arab League," he said. The body would then seek endorsement from Mr Assad's Arab and Western foes in the Friends of Syria group and from the UN General Assembly.
Russia, which views Mr Assad's opponents as pawns of the West, urged the new body to negotiate and to reject outside meddling.
China called for "a political transition process guided by the Syrian people".