Foreign Minister Farouq al-Shara made the pledge in a letter to the UN.
Syria has already begun the withdrawal, following an outcry over the assassination last month of former Lebanese Prime Minister, Rafik Hariri.
The Lebanese opposition accused Syria of being behind the killing, and street protests led to the downfall of the pro-Syrian administration in Beirut.
Prime Minister Omar Karami stood down two weeks after the 14 February bomb blast that killed Hariri.
President Emile Lahoud reinstated him on 10 March, but he has said he plans to quit again on Wednesday after apparently failing to form a national unity government.