UN peace envoy Lakhdar Brahimi, however, insisted on the need for a "political solution" to the three-year conflict, urging an "end to the supply of arms to all parties".
Opposition Syrian National Coalition chief Ahmed Jarba repeated calls on the international community to supply rebels with "sophisticated weapons" as the two-day summit opened.
"I do not ask you for a declaration of war," said Jarba, urging Arab leaders to put pressure on the international community to comply with pledges to supply arms.
A solution to the conflict, in which regime forces have recently made significant advances, requires a "change in the balance on the ground to end the impasse", he said.
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National Coalition spokesman Louay Safi said rebels needed urgently "anti-aircraft missiles" to fend barrel bombs which activists say regime forces have been raining down on fighters and civilians alike.
The conflict in Syria, which in mid-March entered a fourth year, has killed more than 140,000 people and displaced millions.
"Let me say quite frankly that keeping Syria's seat empty... Sends a clear message to Assad that he can kill and that the seat will wait for him," he said.
The Syria government's brutal repression of protests which erupted in March 2011 resulted in its suspension from the 22-member Cairo-based Arab League.
Its seat was allocated to the National Coalition at last year's Arab summit in Qatar, but has not been handed over because the opposition must meet legal requirements, said Arab League chief Nabil al-Arabi.