Syria's government has responded with "constructive interest" to a UN proposal to suspend fighting in the second city of Aleppo, UN envoy Staffan de Mistura said on Tuesday.
An Aleppo representative for the Free Syrian Army (FSA) rebel group, however, effectively rejected the freeze, setting virtually impossible-to-achieve conditions.
"My meetings here with the government and with President (Bashar al-) Assad gave me the feeling that they are studying very seriously and very actively the UN proposal," De Mistura said at a press conference in Damascus.
"The initial response by the government of Syria... was of interest and constructive interest," he added.
"They are now waiting for our contact with the other stakeholders, the other organisations, people with whom we will be talking in order to make sure that this proposal can be moving forward."
On Monday, Assad said he was ready to study the UN plan to "freeze" fighting in Aleppo, which has been divided into government- and rebel-held areas since an insurgent offensive in mid-2012.
De Mistura put the so-called "action plan" forward last month to allow for aid deliveries and to lay the groundwork for peace talks, saying Aleppo would be a "good candidate" for such a freeze.
"All Syrians need a concrete example... That's why we have come to the conclusion of making a specific proposal," he said Tuesday.
"Aleppo city is not far from possible collapse and we need to do something before that happens," he added.
In recent months, government forces have advanced around the outskirts of the eastern portion of the city that is under rebel control, threatening to encircle it completely.
De Mistura stressed that the "freeze" proposal was an "action plan, not a peace plan yet."
"Certainly this is not a substitute for a political solution, but it is an incentive in that direction."
Signup to our newsletter and follow us on Facebook and Twitter!
Rebel-held areas of Aleppo are under the control of multiple groups, including fighters affiliated with the Western-backed FSA.
FSA commander Zaher al-Sakit said in a posting online that any deal would require the release of prisoners, particularly female detainees, an end to regime air strikes, the expulsion of "sectarian terrorist militias" and handover of "the war criminals who used chemical weapons against civilians."
Other groups in the city have been similarly cool, with the powerful Islamic Front declining any comment, and the Jaysh al-Mujahideen group saying it would only back a full political solution, not a local deal.
More than 195,000 people have been killed in Syria since the beginning of the conflict in March 2011, with successive attempts at internationally backed negotiations failing to yield a peace deal.
- Local ceasefires -
Syria's government has already endorsed a policy of negotiating local ceasefires, though the truces have been criticised by activists who say the regime besieges neighbourhoods into accepting deals.
National Reconciliation Minister Ali Haidar told AFP on Monday that local ceasefire deals were in place or being pursued in 50 areas of the country.
The truces "began with a stop (to fighting), the handing over of weapons, the exit of armed men from the affected regions... and the return of residents," Haidar said.
Activists say the regime often imposes strict conditions on neighbourhoods accepting truces, and it has reneged on pledges including the release of detainees in exchange for such deals.
De Mistura, on his second visit to Syria, left Damascus for Beirut on Tuesday and was due to travel on to Cairo the next morning.