Colonel Abdel-Jabbar al-Oqaidi, who defected from the Syrian army six months ago, told Reuters government troops had tried for three days to capture the south-western Aleppo neighbourhood of Salaheddine, and Assad's soldiers were increasingly demoralised.
The fight for Syria's second city has become the focus of the 16-month-old rebellion against Assad, with rebel fighters confronting government forces backed by artillery and helicopter gunships.
"We don't have goals for the coming months. We have goals for the coming days. Within days, God willing, Aleppo will be liberated," said Oqaidi, dressed in green camouflage uniform at an Aleppo school which has been turned into a rebel base.
Describing the growing conflict which has engulfed Aleppo in the last few days as "street war", he said the rebel aim was to capture districts one by one and establish control over them, before taking more territory from the army.
"We secure our areas and then move to other neighbourhoods, pushing towards the city centre," he said, speaking in an interview late on Monday. "God willing, we will liberate Aleppo and its military and security sites."
"The regime's capabilities are also being weakened. They can shell us from afar with tanks and helicopters. But inside their morale is zero," said Oqaidi, head of the Joint Military Council, one of several rebel groups in Aleppo.
An unidentified Syrian army officer told state television on Sunday that his forces had recaptured Salaheddine, which lies on the south-western entrance to Aleppo, and the rest of the city would be under government control within days.
But on Tuesday Syrian television said the army was still chasing what it called "armed terrorists" in Salaheddine.
"The regime has tried for three days to recapture Salaheddine but its attempts have failed and it has suffered heavy losses in human life, weapons and tanks. It has been forced to withdraw," Oqaidi said.
Oqaidi, whose military uniform and boots contrasted with the T-shirts, frayed trousers and sandals worn by the fighters around him, was speaking in what appeared to be the head teacher's office in the school commandeered by rebels.
Rifles at their sides
Down the hall, painted brightly with murals of children playing, men in undershirts were sleeping in the classrooms on mattresses with their rifles at their side.
On the wall, names of rebel battalions were scrawled, along with graffiti by members of the Free Syrian Army (or FSA): "A ruler who kills his people is a traitor" and "Watch out shabbiha, Alawites, the FSA is coming to Aleppo and to Syria."
Assad and many of his army officers are members of the Alawite sect, an offshoot of Shi'ite Islam, as are most of their allied shabbiha militiamen.
With grey, combed-back hair, blue eyes and a moustache, Oqaidi appeared relaxed and comfortable and smiled frequently during the interview. But the former army officer delivered a blunt message.
"You can't stay with this regime and stand watching all the slaughter and shelling they have subjected this country to."
Oqaidi conceded the rebels, who he said numbered more than 3,000 in Aleppo, could not match the army's superior firepower, but he said they did have weapons which could bring down helicopters and destroy tanks.
The charred hulks of tanks around the city partly endorse Oqaidi's comments, though there has been no evidence of helicopters being shot down.
Oqaidi said rebels were working to bring a sense of order to the areas under their control - an arc which stretches from Salaheddine in the south-west to districts on the north-eastern fringe of the city.
"Once we control a neighbourhood we try to keep up administration. That means sending people over to ensure the electricity and water stay on," he said. "We have made sure the bread ovens are still open, we run the bread lines. We check on the hospitals. We have to patrol traffic."
Looking confidently ahead to a rebel drive into the heart of Aleppo, he said reinforcements were already in place for an offensive.
"I haven't been to the city centre in about six months. Of course I can't wait to see it again, to go back and walk near the citadel again."