The CIA (search) is reviewing an audiotape purporting to contain the voice of Saddam Hussein (search) but has not verified that it was the ousted Iraqi leader, a U.S. intelligence official said Friday.

"We can't confirm its authenticity," the official said, speaking on the condition of anonymity. "It's not clear when it was done."

In the tape aired on the Arab television station Al-Jazeera (search) Friday, the voice purporting to be Saddam said he is still in Iraq and directing attacks on American forces there. He called on Iraqis to help the resistance against the U.S.-led occupation.

Reviews of such tapes by the American intelligence community typically include a technical analysis aimed at matching the voice to known recordings of Saddam. That process that can take days.

Experts on Saddam also listen for specific references in the language that would suggest when the message was recorded.

At the height of the war, some U.S. intelligence analysts concluded that many of Saddam's messages were prerecorded before the fighting.

Hard evidence on Saddam's whereabouts and status has been lacking in the weeks since the major fighting ended. But U.S. intelligence analysts believe he is alive and most likely still in Iraq.