According to the agreement, rebels are supposed to turn in their light weapons tomorrow - Thursday - before being transferred to the northwestern province of Idlib on Friday.
Some 150 militants with their families are expected to leave the two besieged towns to the west of the Syrian capital.
However, the 400 militants who chose to stay will have their cases settled.
In August, Syrian government forces entered the rebel-held suburb of Daraya after rebels and their families had been evacuated under a similar agreement.
