Syria has promised to give the UN a timetable next week for the full withdrawal of its troops from Lebanon, says the UN's Middle East envoy.
Crowds threw flowers at troops returning to Syria
Terje Roed-Larsen made the announcement after meeting Syrian President Bashar al-Assad in northern Syria.
In a statement, he said Mr Assad had committed to pull out all Syrian troops and intelligence services from Lebanon.
The talks came after Syrian troops began a partial withdrawal, crossing the border from Lebanon into Syria.
The UN has called for the immediate withdrawal of all 14,000 troops and intelligence personnel.
Syria has come under increasing Western and Arab pressure to withdraw from Lebanon since the assassination of former Lebanese Prime Minister Rafik Hariri last month.
Lebanese opposition groups have blamed Syria for the murder - a charge Damascus vehemently denies.
Question of time
After the talks in the northern city of Aleppo, Mr Roed-Larsen said he would present UN Secretary General Kofi Annan further details of the timetable for a complete withdrawal after arriving in New York early next week.
SYRIA IN LEBANON
Military intervention begins in 1976
30,000 troops in Lebanon during 1980s, currently 14,000
Syrian forces help end Lebanese civil war in 1990 and maintain peace
Calls for Syrian withdrawal increase in 2000 after Israeli pullout from southern Lebanon
UN resolution calling for foreign forces' withdrawal in Sept 2004
He said he was encouraged by President Assad's commitment to the full implementation of Security Council resolution 1559, referring to last September's UN call for the complete withdrawal of all Syrian troops from Lebanon.
"The first stage will see the relocation of all military forces and intelligence apparatus to the Bekaa valley by the end of March," he said in a statement.
"Further, a significant number of these Syrian forces, including intelligence [personnel], will be withdrawn from Lebanon into Syria during this stage," the envoy said.
"The second stage will lead to a complete and full withdrawal of all Syrian military personnel, assets and intelligence apparatus."
No date was gven for this second stage.
But President Assad appears to have met most of the conditions for the withdrawal, says the BBC's Dan Isaacs in Damascus.
But the question remains whether this will be achieved ahead of Lebanese elections in May.
An undisclosed number of the 6,000 troops deployed in Lebanon's Bekaa Valley crossed into Syria in a convoy overnight.
Our correspondent at the Jdaidet Yabous border point says crowds of government supporters were bussed to the frontier for a carefully stage-managed occasion.
Troops came out of the night and through heavy snow, and had flowers thrown by crowds as they passed by.
About 60 vehicles passed through the border overnight, including a range of covered trucks, along with buses and jeeps.
Syria has stationed troops in Lebanon since 1976, when it was asked to intervene by one of the factions fighting in the civil war.