The Syrian regime is ready to suspend aerial bombardment of Aleppo to allow a humanitarian ceasefire, a UN envoy said, even as government troops sought to encircle embattled rebels.
The comments by Staffan de Mistura on Tuesday came as regime forces cut the main rebel supply line into Aleppo in fighting that killed more than 150 people.
As clashes raged in the area, De Mistura announced that Damascus was willing to suspend its aerial bombardment of Aleppo city for six weeks.
"The government of Syria has indicated to me its willingness to halt all aerial bombing and artillery shelling for a period of six weeks all over the city of Aleppo from a date we'll announce from Damascus," De Mistura told journalists after addressing the UN Security Council.
Rebel fighters, who have no air power, would be asked to suspend rocket and mortar fire for six weeks.
"The purpose is to spare as many civilians as possible while we try to find a political solution," the diplomat said.
De Mistura was appointed UN peace envoy for Syria in July and last year proposed a plan to "freeze" fighting in Aleppo that has thus far failed to gain much traction.
He incurred the wrath of the opposition last week by describing President Bashar al-Assad as "part of the solution" to the country's conflict.
An activist in Aleppo expressed doubt about the ceasefire plan, saying efforts by De Mistura and others "have simply given the regime more time to kill more civilians."
"Meanwhile, the regime is bringing military supplies and reinforcements to Aleppo on a daily basis," he told AFP.
- Rebel supply route cut -
On the ground, meanwhile, Syrian troops effectively severed the main rebel supply route into the eastern half of Aleppo city, which is under opposition control, the Syrian Observatory for Human Rights said.
The highway runs up to the Turkish border but regime forces now control two villages straddling the route, effectively closing it to rebel traffic.
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Aleppo city has been divided between regime control in the west and rebel control in the east since shortly after fighting began there in mid-2012.
In the surrounding countryside the situation is largely the reverse, with rebels controlling much of the area west of the city and regime forces much of the east.
The severing of the highway leaves the rebels with only a long detour through the countryside available to them for resupply.
Regime forces also captured the village of Hardtaneen, in the countryside of Aleppo, but lost another village to rebel fighters in the area, the Britain-based Observatory said.
The fighting left more than 150 people dead, the monitor reported, including at least 70 members of the regime forces, both army troops and foreign and local militiamen.
At least 86 opposition fighters were killed, including 20 from Al-Qaeda's Syrian affiliate Al-Nusra Front.
On Monday, regime troops opened fire on two towns on the road to Nubol and Zahraa, government-held Shiite villages that have been under rebel siege for more than 18 months.
"The regime troops have two goals in the area: to cut the road leading from Aleppo to the Turkish border, which is the key supply road for the rebels, and to open the way to Nubol and Zahraa," Observatory director Rami Abdel Rahman said.
In a statement issued late Tuesday, the army said it had taken "control of large regions in northern Aleppo province and the last terrorist routes to Turkish territory".
"The army has imposed a cordon around the terrorist positions that attack the residents of Aleppo city."
Elsewhere in the country, the Observatory said Kurdish forces had now seized more than half the villages around the flashpoint town of Kobane from IS militants.
The group said fighters from the Kurdish People's Protection had captured 215 villages around the border town, which fell to them on January 26 after more than four months of fighting.
More than 210,000 people have killed in Syria since the conflict began in March 2011 with anti-government protests that spiralled into a multi-sided civil war after a regime crackdown.