The videotape, aired Wednesday on the Arab al-Jazeera television network, has two voiceovers, one purportedly from bin Laden, and the other from his deputy, Ayman al-Zawahri. A CIA official, who spoke on the condition of anonymity, said agency analysts have determined that al-Zawahri's voice is authentic.
But the technical analysis of the section with bin Laden's voice is inconclusive, the official said. The analysis will continue, but the official acknowledged the CIA may not be able to make a final determination.
In speaking, al-Zawahri mentions the war in Iraq, which suggests it was recorded sometime since the fighting started in March. The voice purported to be bin Laden's speaks only of some of the Sept. 11 hijackers but makes no reference to more recent events.
U.S. intelligence officials said the tape is regarded as al-Qaida propaganda aimed at capitalizing on the Sept. 11 anniversary. Such messages let the network's rank-and-file know the leadership is still viable, officials said.
Officials also said messages from al-Qaida leaders sometimes presage an attack.