Syria, which has held military and political sway in Lebanon for the past three decades, has promised to complete its troop withdrawal by the end of April in the face of intense international pressure.
UN Resolution 1559, which was adopted in September, calls for the pullout of all foreign forces from Lebanon, the end of foreign interference in its internal affairs and the disarming of militias.
At the United Nations, spokesman Stephane Dujarric said on Friday that UN Secretary-General Kofi Annan was due to deliver his report on the implementation of the resolution to Security Council members no later than 26 April.
Syria's decision to withdraw came after the 14 February bomb blast that killed al-Hariri, and which was blamed by many on the Lebanese government and its political masters in Damascus.
The United Nations is also mounting an international commission to probe the killing, which sparked widespread protests that brought down the Lebanese government in late February.