In what appeared to be a face-saving address to the Syrian parliament, Assad said his plan would put Syria in full compliance with international requirements.
"Our way is a gradual and organized withdrawal," he told lawmakers, adding that Syria has "an interest" in withdrawing from Lebanon.
"By carrying out this measure, Syria will have fulfilled requirements of the Taif agreement and implemented U.N. Resolution 1559."
The 1989 Arab-brokered Taif Accord called for Syria to move its troops to the Lebanese border and for both countries to then negotiate the withdrawal.
The U.N. resolution, drafted by the United States and France in September, called on Syria to withdraw its forces from Lebanon, stop influencing politics in the country and allow Lebanon to hold presidential elections as scheduled.
Syria has had troops in Lebanon since 1976, when they were sent as peacekeepers during that country's 1975-1990 civil war.
President Bush said Friday that anything less than a full withdrawal by May when parliamentary elections are to be held would be an unacceptable "half-measure."
"We will withdraw our forces stationed in Lebanon fully to the Bekaa region (in the east) and later to the Lebanese-Syrian border areas," he said to cheers from legislators in the chamber and from thousands of Syrian supporters listening outside the building.
In the cleverly worded address, Assad said, "We would not stay one day if there was Lebanese consensus on the departure of Syria," failing to state that Damascus wields decisive influence with Lebanese officials.
The Lebanese people are sharply divided over the presence of Syria's soldiers. Massive protests in past weeks have demanded Syria's withdrawal and led to the resignation of the pro-Syrian government last week.
President Emile Lahoud, a staunch Syrian ally, is expected soon to announce consultations for a new prime minister after the government was dissolved last week with the resignation of Prime Minister Omar Karami.