The nationwide cease-fire is to begin at midnight local time. Russia and Turkey will act as guarantors. The agreement does not include areas under the control of ISIS.
In some areas of Syria, local truces have averted deadly military takeovers. But in a suburb north of Damascus, rebel fighters say their departure resulted more from coercion than negotiation.
Evacuations of civilians and rebel fighters from east Aleppo finished on Thursday night, and forces supporting President Bashar Assad seized the enclave. But the rebels' surrender doesn't mean peace.
Remaining rebels and civilians in east Aleppo wait in freezing weather for transportation out of the city; a few hundred people refuse to leave. Pro-regime forces might enter as soon as this evening.
Talks in Moscow between Russia, Turkey and Iran on Syria's future went ahead despite the assassination in Ankara of Russia's top diplomat. Moscow laid blame for the killing farther afield.
Turkey identified the gunman as Mevlut Mert Altintas, a 22-year-old riot police officer who shouted, "Don't forget Aleppo!" Seven people were arrested Tuesday, and one was later released.
Multiple cease-fires have failed and evacuation efforts halted in the dwindling rebel-held enclave in Aleppo, partly over disputes about two regime-friendly villages. Now buses are moving again.
Evacuations had been set to resume Sunday as the U.N. Security Council prepares to vote on a resolution that calls for sending international monitors to the besieged city.
Syrian state TV said thousands of fighters and civilians await evacuation from rebel-held eastern Aleppo. Some ambulances came under brief fire, but now buses of evacuees are leaving the city.