"Tomorrow everything will be over," the officer, speaking on condition of anonymity, told The Associated Press on Saturday.
He did not elaborate, but it appeared that the withdrawal would include the Anjar base in eastern Lebanon occupied by Syria's chief of military intelligence in Lebanon, Major General Rustom Ghazale.
The same officer said earlier this week that Ghazale would evacuate Anjar by Tuesday.
On Saturday night, the largest number of Syrian troops to leave Lebanon in one batch vacated at least 10 positions in the northern part of the Bekaa Valley in eastern Lebanon.
Under pouring rain, dozens of trucks carrying hundreds of soldiers and 150 armored vehicles towing cannons and rocket launchers were seen heading to the Lebanese-Syrian Masnaa border point, witnesses said.
Syria began withdrawing its troops from Lebanon last month after the 14 February assassination of former prime minister Rafiq al-Hariri. The assassination, for which the Lebanese opposition blamed Lebanese authorities and its Syrian backers, threw Lebanon into political turmoil, driving out the pro-Syrian government and forcing Syria to begin its withdrawal.
Syria and Lebanon have denied involvement in the killing.
Last week, Lebanese and Syrian officials said the remaining 1000 troops would be gone by 26 April. The force stood at 14,000 troops in February, indicating the swiftness of the pullout.
Secretary-General Kofi Annan said last week that he was delaying the release of a report on Syria's withdrawal from Lebanon until Tuesday so the UN could confirm the pullout of all Syrian forces.
Annan's chief of staff said Wednesday that Annan had spoken to Syrian President Bashar al-Asad and was "very optimistic" that all troops and intelligence operatives would be out of Lebanon by Tuesday.
In September, the UN Security Council adopted a resolution calling on Syria to withdraw all its troops and intelligence operatives.
The United States has also been pushing Syria to withdraw its troops from Lebanon and stop interfering in the country's politics.
Syria sent troops to its smaller neighbor in 1976 to help quell a civil war, but the troops remained after the war ended in 1990.