It appeared that Terje Roed-Larsen was able to obtain a timetable from Assad, which he did not make public.
"I will present (U.N.) Secretary General Kofi Annan with further details of the timetable for a complete Syrian pullout from Lebanon upon my arrival in New York early next week," Roed-Larsen said in a statement after meeting with Assad in the northern city of Aleppo.
"The meeting was very constructive and I am much encouraged by President Assad's commitment to the full implementation of Security Council resolution 1559," he said.
"The president has committed to withdraw all Syrian troops and intelligence from Lebanon in fulfillment of Security Council resolution 1559," Roed-Larsen said in the statement read to The Associated Press by his spokesman Najib Friji.
The meeting in Aleppo, some 220 miles north of the capital Damascus was attended by Foreign Minister Farouk al-Sharaa and his deputy Walid al-Moualem, the Syrian Arab News Agency, SANA, said.
Roed-Larsen's visit comes after Syria began this week, under international pressure, pulling its 14,000 troops back to the eastern Bekaa Valley. It plans to negotiate later with the Lebanese government on their complete removal from Lebanon.
But U.N. associate spokeswoman Marie Okabe said in New York that Roed-Larsen was going to the region "to have a constructive dialogue" and "was not operating with the use of threats."
U.N. Security Council Resolution 1559 calls for, among other things, an immediate withdrawal of Syrian troops from Lebanon. U.S. President George W. Bush wants Syria to move out before Lebanon's parliamentary elections scheduled to take place in April and May.
The U.N. Security Council is to receive a report next month from U.N. Secretary-General Kofi Annan, based on Roed-Larsen's visit, on Syria's implementation of the resolution. It then will consider next steps, which as a last resort could include sanctions on Syria if it deems the country to have flouted the demands.
Despite the pullout from the north of Lebanon, nine Syrian intelligence offices remain open there, including in the towns of Tripoli, Akkar, Minye and Amyoun. Plainclothes intelligence agents operate from the guarded offices in apartment buildings and deal directly with Lebanese.
Witnesses said all Syrian intelligence officers in the mountain towns of Aley and Bhamdoun east of Beirut withdrew Saturday and headed to Hammana high in the mountains. However, Syrian intelligence offices were still in Beirut and northern Lebanon late Saturday.
On March 5 Assad announced a two-stage pullback of Syrian forces from Lebanon. Syrian and Lebanese presidents agreed a day later that Syrian troops will redeploy to the eastern Bekaa Valley by the end of March but did not say when they will withdraw from Lebanon completely.
Roed-Larsen said the redeployment to the Bekaa Valley before the end of this month will include the withdrawal of "a significant number of these Syrian troops, including intelligence," from Lebanon into Syria.
"The second stage will lead to a complete and full withdrawal of all Syrian military personnel and the intelligence apparatus," said the U.N. envoy, who added that he will continue his dialogue with Assad and other concerned parties.
Roed-Larsen's visit to Syria is the fourth leg in a Middle East tour that has already taken him to Egypt, Jordan and Lebanon, to which he would return following his meetings with Syrian officials.
Syria has made six redeployments since 2000.
Early Saturday, some 1,000 troops entered Syria in the first batch to come back home since the latest redeployment began Tuesday.
Syria sent troops to its smaller neighbor in 1976 to help quell a year-old civil war. The troops, at times numbering more than 35,000, remained after the war ended in 1990.
Meanwhile in Beirut, around 11,000 people from opposition groups carrying colored paper boards gathered across the street from Hariri's tomb in the central Martyrs Square to form a huge Lebanese red, white and green flag. They chanted "freedom, truth, national unity."
Also Saturday, Syria harshly attacked Jordanian Foreign Minister Hani al-Mulqi for remarks he had made recently in Tel Aviv after a meeting with Israeli Prime Minister Ariel Sharon in which he called on Syria to implement resolution 1559.
Al-Mulqi said he also considered the 1989 Taif agreement that ended the war in Lebanon part of the past and no longer valid, the government Tishrin daily said.
Tishrin said in an editorial that al-Mulqi, "has bypassed even the United States and Israeli stands and also U.N. resolution 1559 that is based in some of its items on the Taif Agreement." In Jordan, Al-Mulqi told the Associated Press that Tishrin's remarks were "nonsense."
"We cannot be selective in implementing U.N. resolutions," al-Mulqi said. "Tishrin can say whatever it wants to say."