Ramzi Ezzedine Ramzi, deputy to the UN envoy to Syria, Staffan de Mistura, is to hold a series of meetings in Damascus, their spokeswoman Juliette Touma told AFP via the Internet.
At the start of the week, De Mistura held what Touma termed "constructive" talks on Aleppo with rebel groups in Gaziantep, Turkey.
In late October, he had announced a plan for a "freeze" in fighting, following a series of failed international efforts to negotiate an end to the Syrian conflict, which erupted in March 2011.
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He has since said the northern city of Aleppo is a "good candidate" for the bid.
The city has been divided between regime control in the west and rebels in the east since mid-2012.
Syrian Foreign Minister Walid Muallem has called for rebels to hand over their heavy weapons and allow the return of local administration officials to Aleppo under any deal.
For their part, the rebels want guarantees of an effective freeze on the ground and that government forces are not redeployed from Aleppo to the flashpoint Eastern Ghouta region near Damascus.