"It is likely the battle for Aleppo will start in the coming hours or days, and its aim is to reclaim the towns and villages in the province," the source told AFP on condition of anonymity.
The Syrian Observatory for Human Rights has reported the regime was deploying "thousands of soldiers" in Aleppo province, aiming to recapture rebel posts and sever supply routes from neighbouring Turkey.
On the international front, Britain said Syrian government gains on the ground had made organising peace talks harder, as Israeli Prime Minister Benjamin Netanyahu and Russian President Vladimir Putin discussed Syria's conflict by telephone.
The announcement of a potential new offensive comes five days after the army expelled rebels from Qusayr in central-west Syria.
Syrians were shown on Sunday firing into the air and waving portraits of President Bashar al-Assad in Qusayr to celebrate the government's victory, in footage broadcast by Hezbollah's Al-Manar television.
Syrian daily Al-Watan said the army has "started to deploy at a large scale in Aleppo province, in preparation for a battle that will be fought in the city and its outskirts".
Rebels last July launched a massive assault on Aleppo, once Syria's commercial hub. The city has since suffered daily regime bombardment and clashes.
Al-Watan also said "the Syrian army will take advantage of its experience in Qusayr and Eastern Ghouta (near Damascus) to advance in the (central) province of Hama and Homs" nearby.
In Beirut, a Lebanese Shiite student leader was shot in the back and fatally wounded outside Iran's embassy during a demonstration against the Iranian-backed Hezbollah, a security official and a Shiite politician said.
It was not known who fired the deadly shot.
Around 100 people also staged an anti-Hezbollah protest in central Beirut amid a heavy security presence, an AFP journalist said.
The Lebanese Red Cross, meanwhile, said dozens of people wounded in Qusayr have been brought across the border for treatment.
"Eighty-seven wounded Syrians were transported by the Lebanese Red Cross from Friday afternoon to Sunday morning to hospitals in Bekaa (east) and to north" in Lebanon, said Georges Kettane, operations director of the LRC.
International Committee of the Red Cross official Robert Mardini warned that the refugees "who have already arrived may only represent the tip of the iceberg".
"We don't have information on how many people have been wounded or killed, or on the number of people who remain in Qusayr," he said.
British Foreign Secretary William Hague said Syrian regime gains made it harder to organise a US-Russian proposed peace conference.
"The regime has gained ground on the ground, again at the cost of huge loss of life and the indiscriminate use of violence against the civilian population," he told BBC television.
"That makes the Geneva conference harder to bring about and to make a success."
In Jerusalem, the premier's office said Netanyahu had spoken to Putin after Russia offered to bolster the beleaguered UN peacekeeping force monitoring the Israeli-Syrian ceasefire line on the Golan Heights.
"We discussed issues linked to Syria where the situation is becoming more complex by the day," Netanyahu said.
"We saw only last week the battles which took place next to our border on the Golan," he said after Syrian rebels clashed with Assad's forces for control of Quneitra in the demilitarised zone.
Thursday's clashes, in which two UN peacekeepers were lightly wounded, prompted Austria to announce it would withdraw its 377 troops from the UN Disengagement Observer Force.
On Sunday, the Syria conflict also spilled over into Iraq, where a guard was killed and two were wounded in clashes with Syrian rebels near a border crossing.
The Syrian Observatory, meanwhile, said Islamist rebels fighting the regime shot dead a 15-year-old in front of his parents and siblings on Sunday in Aleppo after accusing him of blasphemy.
More than 94,000 people have been killed and some 1.6 million Syrians have fled the country since March 2011 after Assad cracked down on pro-democracy protests, the watchdog estimates.