Russia and Syria agreed to stop bombing Aleppo for eight hours on Thursday so humanitarian aid could reach the city.
Civilians were getting relief in September before a U.N. convoy was attacked, killing 20 people. The attack was blamed on Russia, which denied any wrongdoing, and aid was suspended.
Then, Russia and Syria resumed bombing rebel-held areas supported by Western nations.
Airstrikes have killed hundreds of people in the past month, including many children.
Thursday's brief cease-fire may be a small victory for the U.S. and European Union, which have demanded Russia and Syria stop bombing Aleppo. But it's well-short of the total cease-fire the West has been pushing for.
A United Nations official said Monday, "If we cannot find a solution [by December], Aleppo will not be there anymore."
Eight hours might not be enough time. The U.N. said aid convoys require 12 hours to reach those in need.