Rebel fighters have made gains across the country in the last month, seizing military bases and taking on Mr Assad's better-armed forces on the fringes of his powerbase in Damascus.
Activists said fighting raged in southern Damascus near the international airport and reported clashes in the northern Damascus districts of Rukneddine and Salhiyeh – the heaviest there since the uprising began 20 months ago.
Despite using more effective battlefield tactics and acquiring more arms, the mainly Sunni Muslim fighters have so far lacked the fire-power to deliver a decisive blow to Assad.
Abu Moaz al Agha, a leader and spokesman of the powerful Gathering of Ansar al Islam, which includes many Islamist rebel brigades, said the new, Islamist-dominated military command elected in Turkey over the weekend could change that.
"What we need now is the heavy weapons and we expect to get them after the formation of this."