The announcement of the upcoming message came as al-Qaida released a new video in which bin Laden's deputy, Ayman al-Zawahri, boasted that the United States was being defeated in Afghanistan, Iraq and other fronts.
Speakers in the video promised more fighting in Afghanistan, North Africa and Sudan's Darfur region.
The messages are part of a stepped-up propaganda campaign by al-Qaida around the anniversary of the Sept. 11, 2001 attacks against the World Trade Center and the Pentagon. Earlier this month, bin Laden released two messages — including his first new appearance in a video in nearly three years.
A banner posted on an Islamic militant Web site on Thursday advertised that another message would be released, though it did not say whether bin Laden would appear in video or speak in an audiotape.
"Soon, God willing: 'Come to Jihad (holy war)', from sheik Osama bin Laden, God protect him" the banner read.