The ceasefire does not go into effect for a week, and although the Syrian opposition expressed "cautious optimism", it also said more innocent civilians would be killed in that time.
Government forces, aided by a withering Russian bombing campaign, are trying to encircle rebels in Syria's largest city of Aleppo and cut off their supply route to Turkey. Another week of fighting could bring the Syrian troops closer to that goal.
Syrian forces recaptured several strategic hills north of Aleppo and are in position to target the final supply line to the rebel-held eastern suburbs, according to Al-Manar TV, a Lebanese channel run by the militant group and Syrian ally Hezbollah.
US Secretary of State John Kerry praised the ceasefire agreement, made after a meeting in Munich, as a "significant accomplishment" in the five-year war, but he noted more work would be needed to turn it into a fully fledged ceasefire.
If the Syrian Government and the Opposition agree to the ceasefire details, that could pave the way for a new round of peace talks between President Bashar Assad's Government and the Opposition, scheduled for February 25 in Geneva.
Russian Foreign Minister Sergey Lavrov made it clear Moscow will continue airstrikes on Aleppo and other parts of Syria because they are targeting groups not eligible for the "temporary cessation of hostilities".
A member of Assad's ruling Baath Party said operations will continue against the Isis groups, the Nusra Front, and other factions that are close to them.
Parliament member Sharif Shehadeh said "the army aims to regain all Syrian territories and any part of Syria is a target for the army".
Syrian aircraft dropped leaflets over parts of Aleppo province telling militants to "drop your arms or this will be your fate". They bore a photo of the nearly naked, bullet-riddled body of a fighter and a Kalashnikov assault rifle by his side.
"The belt is narrowing around you more and more. Go back to where you came from," the leaflet read.
Kerry and Lavrov also announced an agreement to "accelerate and expand" deliveries of humanitarian aid to besieged Syrian communities beginning this week.
A task force began its first meeting in Geneva, and its leader, Jan Egeland, said he hoped it could pave the way for aid to be delivered to besieged areas in Syria "without delay".
Sustained delivery of assistance is expected to "begin this week to besieged areas where civilians are in desperate need of assistance. Humanitarian access to these most urgent areas will be a first step toward full, sustained and unimpeded access throughout the country."