Rebels and government forces in Eastern Ghouta plan to announce a ceasefire shortly, according to the UK-based Syrian Observatory for Human Rights.
The “test period” truce near Damascus could potentially be extended if initially successful, Reuters reported.
The talks between opposition rebels and Bashar al-Assad are believed to be the first of their kind, instigated by Iranian and Russian mediators.
“A ceasefire in Eastern Ghouta would begin at 6:00 am (0400 GMT) Thursday and will last 15 days,” Rami Abdel Rahman of the Observatory said.
Jaish al-Islam, a rebel group with a strong presence in the area, was one of the primary negotiating partners, Rahman added.
The rebel stronghold of Eastern Ghouta is frequently bombed by government forces.