The German government is planning to send up to 1,200 troops to help in the fight against the Islamic State group.
Defence Ministry spokesman Jens Flosdorff said that the figure would be an "upper limit" for the number of troops needed to provide support for and operate reconnaissance aircraft, tanker planes and a warship.
The Cabinet is due to agree the mission's mandate on Tuesday and put it to Parliament for approval. German troops will not actively engage in combat.
Officials rejected any suggestion that Germany might cooperate with troops loyal to Syrian president Bashar Assad in the fight against IS.
But Foreign Ministry spokesman Martin Schaefer said that "if the Syrian regime says it's fighting terrorists on its own territory, then it should do so, please."