The speech to the People's Assembly had not been previously scheduled. The official said from Damascus on Friday that al-Asad's address will "deal with the situation in the region and the ongoing developments". He did not elaborate.
Al-Asad is expected to announce a pullback of troops to eastern Lebanon, near the Syrian border, but not a full withdrawal, the Lebanese defense minister said Friday.
"No one knows what President Asad will say except the president himself, but we expect President Asad to announce a redeployment to the Bekaa region," Lebanese Defense Minister Abdul-Rahim Murad, a member of the pro-Syrian government in Beirut, told The Associated Press.
He answered "No" when asked whether the redeployment meant a full withdrawal.
He said the redeployment would be in line with the Taif Accord, a 1989 Arab-brokered agreement that called for a pullback to the border and eventual withdrawal.
Such a step would appear to fall short of US and Arab demands for a complete removal of Syria's forces from Lebanon, where Damascus has held sway for more than a decade.
In the Taif agreement, Syrian forces are to redeploy to the eastern Bakaa Valley before Lebanese and Syrian governments agree on a timeline on how long these forces should stay.
Al-Asad told Time magazine in an interview published this week that Syria's 14,000 troops might pull out of Lebanon in the next few months, the timing being technical rather than political.
Saudi Arabia added a key Arab voice on Thursday to mounting demands that Syria withdraw its troops swiftly from Lebanon.
Another Arab heavyweight, Egypt, also wants al-Asad to pull out his troops.