In an interview with Syrian daily Al-Watan to be published tomorrow, an early copy of which was seen by AFP, Assad said defeating beleaguered rebels in Aleppo would not put an end to Syria's conflict.
"It's true that Aleppo will be a win for us, but let's be realistic - it won't mean the end of the war in Syria," Assad said.
"But it will be a huge step towards this end," he said.
Increasingly cornered in a pocket of territory in the city's southeast, opposition factions today called for an "immediate five-day humanitarian ceasefire".
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When asked about the possibility of a truce in Aleppo, Assad said, "it's practically non-existent, of course."
"The Americans in particular are insisting on demanding a truce, because their terrorist agents are now in a difficult situation," Assad told Al-Watan.
He said a rebel loss in Aleppo "will mean the transformation of the course of the war across Syria."
But since violence broke out there four years ago, the city has been left divided between rebels in the east and government forces in the west.
Rebel fighters, who took control of east Aleppo in 2012, have suffered a string of defeats in recent days, losing about 80 per cent of their former territory in the city, according to the Syrian Observatory for Human Rights monitoring group.
Regime forces scored an important victory today when the rebels retreated from the Old City, the historic heart of Aleppo.
Syria's conflict erupted in March 2011 with widespread demonstrations but has since turned into a brutal multi-front war drawing in world powers.