A voice purported to be Al Qaeda's second-in-command warned in an audiotape that the terror group will target Americans "in their homeland" and will drive the U.S. military from bases in the Middle East.

Excerpts of the 10-minute tape were broadcast Friday by satellite television channel Al-Jazeera. It said the recording was made by Ayman al-Zawahri (search), Usama bin Laden's deputy, and that it received the tape earlier Friday through the mail.

In Washington, the CIA said it believes the tape is authentic. An Egyptian lawyer who knows al-Zawahri, Montasser el-Zayat, said the broadcast was undoubtedly his voice.

The speaker mentioned a visit to Iraq by U.S. Deputy Defense Secretary Paul Wolfowitz (search) that took place in late October. However, there was no reference to last weekend's capture of ousted Iraqi leader Saddam Hussein, indicating the tape may have been made before that.

The speaker denied the resistance U.S. troops face in Iraq comes mainly from Saddam loyalists and said insurgents there are "holy warriors."

"It is a real and authentic holy war of the Iraqi people," he said.

The speaker also mentioned the battle of Tora Bora (search), a major clash between U.S.-led forces and Al Qaeda fighters in the mountains of eastern Afghanistan.

"Two years after Tora Bora, the American bloodshed started to increase in Iraq, and the Americans have become unable to defend themselves or even defend their big criminals such as Wolfowitz," he said.

That comment referred to an Oct. 26 rocket attack that barraged the Baghdad hotel where Wolfowitz was staying. A U.S. colonel was killed, but Wolfowitz escaped unharmed.

"We are still chasing the Americans and their allies everywhere, even in their homeland," he said.

The weeks before and after the rocket attack on Wolfowitz saw a surge in attacks on U.S. forces in Iraq, making November the bloodiest month for U.S. forces since the fall of Saddam. Attacks lessened as the U.S. military launched an offensive in late November. Violence has continued after Saddam's capture on Dec. 13.

Al-Jazeera's newscaster quoted the tape as saying: "Those renegades who offered the Americans military bases and support to kill Muslims should prepare for the day of settling scores because the Americans are ready to flee."