Syrian troops have begun a withdrawal from southern and northern Lebanon, the Lebanese defence chief has said.
A date for a full withdrawal of Syrian troops has not yet been given
It comes hours after hundreds of thousands of people gathered in Beirut to applaud Syria's role in the country and reject Western "interference".
US President George W Bush responded by repeating demands for Syria to leave.
Defence minister Abdul-Rahim Murad said Syrian forces would move to the eastern Bekaa valley from Tuesday evening but no date for full withdrawal was given.
Mr Murad said the redeployment of some 6,000 troops to the Bekaa would take a week to 10 days, according to the AFP news agency.
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
The move came after a meeting in Damascus of a joint Syrian-Lebanese military committee, amid mounting international pressure.
The withdrawal is thought to include Syria's intelligence personnel, including their headquarters in Lebanon's capital, Beirut, news agencies reported.
Deputy Prime Minister Issam Fares told Lebanon's LBC television channel that the Syrians' move to the country's eastern region should be completed by 23 March.
Hours earlier, the head of the Syrian-allied Hezbollah group had warned the US, which has been leading demands for a Syrian withdrawal, not to interfere in Lebanon.
"We are here to thank Syria, which has stayed by our side for many years," Hassan Nasrallah told cheering supporters at the huge pro-Syria rally in Beirut.
'Free and fair'
Organised by Hezbollah, a powerful political and military organisation of Shia Muslims, the demonstration dwarfed previous opposition protests urging Syrian troops to leave.
Mr Nasrallah said there would be further demonstrations in other Lebanese towns, including Tripoli in the north, Nabatiya in the south and in the eastern Bekaa valley.
Meanwhile, in a speech in Washington, President George W Bush reiterated US demands for complete Syrian withdrawal before a parliamentary ballot in May.
"Freedom will prevail in Lebanon," he said. "All Syrian military forces and intelligence personnel must withdraw before the Lebanese elections for those elections to be free and fair."
Hundreds of thousands of pro-Syrian demonstrators rallied in Beirut
Mr Bush did not comment on the pro-Syria rally, but White House spokesman Scott McClellan said he was pleased the demonstration - and a rival opposition protest a few streets away - had been peaceful.
The US has described the pull-back plan adopted by Lebanese and Syrian leaders in Damascus as a "half-measure".
Washington said all Syrian troops and intelligence officers should leave Lebanon immediately in line with UN resolution 1559, sponsored jointly by Washington and Paris.
Syrian troops arrived in neighbouring Lebanon as peacekeepers during the 1975-1990 civil war. Since then, Damascus has kept a firm hold on the political and financial spheres in Lebanon.
France, Germany and Russia have also called for a Syrian withdrawal, as has its long-standing Arab ally, Saudi Arabia.
On Monday, large crowds gathered in Martyrs Square for protests to mark three weeks since the death of former Prime Minister Rafik Hariri, killed in a car bomb blamed by many on Syria. Damascus has consistently denied responsibility.