Syria has come under international pressure to end its 29-year military presence since the 14 February assassination of Lebanese former prime minister Rafiq al-Hariri.
"The date and timetable will be announced tomorrow, Sunday, after it is given to UN envoy Terje Roed-Larsen," said the source.
Syrian Foreign Minister Faruq al-Shara and Roed-Larsen will hold a joint news conference at 11.30am (0830GMT) on Sunday after the UN envoy has met President Bashar al-Asad.
The source added that a Lebanese-Syrian military committee had met in Beirut and Damascus in the past few days to agree on the timetable.
"My last meeting with President Bashar al-Asad was good and bore significant fruit and I do expect that this also will be the result of the upcoming talks," Roed-Larsen said in the Egyptian resort of Sharm al-Shaikh on Saturday before meeting President Husni Mubarak.
In Beirut, a military source said Lebanese army chief General Michel Sulaiman held talks with al-Asad in Damascus on Saturday but gave no details of what they discussed.
In September, the UN Security Council adopted a resolution sponsored by the United States and France that demanded that all foreign forces leave Lebanon and all militias there disarm.
Syria first sent troops to Lebanon in 1976, early in its neighbour's 16-year civil war, but in recent years had reduced their numbers to about 14,000 from a peak of 40,000.
Last month, al-Asad announced plans for a two-phase troop withdrawal within the framework of the 1990 Taif Accord that ended the civil war. The first stage, under which all Syrian forces pulled back to the eastern Bekaa Valley and some crossed the border, was completed last month.
Troops and intelligence agents have continued to withdraw since then, but it is not clear how many remain.
Syria promised the United Nations this week that it would complete its pullout before Lebanese parliamentary elections that were due to have taken place in May. The polls might be pushed back because of political turmoil since al-Hariri's death.
A UN spokesman in Beirut said Roed-Larsen would hold talks with Egyptian and Jordanian officials on Saturday before flying to Damascus later in the day. He would go to Lebanon on Monday.
Iranian minister's visit
Also on Saturday, al-Asad met Iran's foreign minister for talks on Lebanon and the war in Iraq.
Al-Asad's talks with Kamal Kharazi come amid Washington's claims that Iran is pursuing a nuclear weapons programme.
Iran's foreign minister (R) meets
Syrian President al-Asad
Iran and Syria are close allies that have both been accused by the United States of supporting anti-Israeli groups, particularly the Lebanese Shia Muslim Hizb Allah.
Kharazi, who arrived in Damascus on Saturday, also held talks with al-Shara.
Syrian's state-run Sana news agency quoted Kharazi as saying al-Hariri's killing was a "painful incident".
Kharazi accused some parties, without naming them, of attempting to "fish in murky water," adding such parties do not want to help Lebanon, Sana said.
Kharazi appeared to be referring to Christian anti-Syrian groups.
On Iraq, Syria and Iran underlined the importance of supporting the process of peace in their war-ravaged neighbour and maintaining its territorial unity.
Some Iraqi officials have accused Syria and Iran of supporting insurgents in fighting US-led troops and Iraqi security forces in Iraq, a claim that both states denied.