CIA thinks tape 'likely' voice of al-Zawahiri
Ayman al-Zawahiri is believed to be No. 2 in the al Qaeda terrorist network.
A swift interrogation would follow if al-Zawahiri is caught.
CNN's exclusive video of al-Zawahiri, some of it never before shown.
The Pakistan border is akin to the 'Wild West.'
Position: Osama bin Laden's closest adviser
Status: Wanted, $25 million reward
Background: Medical doctor; founder of Egyptian Islamic Jihad; referred to as the "brains of al Qaeda"
WASHINGTON (CNN) -- A CIA spokesman said Friday that the voice on an audiotape broadcast by an Arabic language TV channel is "likely" to be that of al Qaeda's No. 2 man, Ayman al-Zawahiri.
The CIA routinely analyzes such tapes to ascertain authenticity.
The spokesman said, "It is not clear when it was recorded," adding that the reference to Pakistani troops being in the tribal areas near the Afghan border could have been recorded any time in the past month or even longer.
The tape calls on Pakistanis to overthrow President Pervez Musharraf -- a key ally of the United States in the war on terror.
"Every Muslim in Pakistan must do his or her best in getting rid of this government, which cooperates with the enemies," the speaker on the tape says.
The Arabic news network Al-Jazeera broadcast the taped statement Thursday.
The tape calls Pakistan's relatively automomous tribes in the northwest border region to resist government forces sent to search for al Qaeda fighters.
"These tribes, which defended Islam throughout all of its history, will not give up to one slave of America," the speaker says.
He also calls Musharraf a traitor and "Muslim assassin."
"After he played his deceiving role in killing thousands of Muslims in Afghanistan, the Americans began giving him new duties," the voice says.
The speaker says Musharraf is helping the United States and its allies "suppress the Muslim nation" by cutting support for Islamic militants in Kashmir and betraying Pakistan's nuclear secrets.
In recent weeks, large numbers of Pakistani forces have moved into the mountainous tribal areas, where U.S. intelligence officials suspect al-Zawahiri and bin Laden may have taken refuge.
Last Thursday, Musharraf said Pakistani troops had cornered a "high-value target" in the region, and other Pakistani officials said they suspected that target was al-Zawahiri. But they backed away from those reports as the standoff and fighting continued through the weekend.
The voice on the tape does not mention the region where the fighting has been taking place, Waziristan, but it does mention two different tribes of the area.
The tape appears to have been recorded later than February, when Pakistan's military the troops into the mountains.
The tape attempts to appeal to Pakistanis' pride by saying that surprise searches, arrests and other operations being conducted by the Pakistani military along the border are insulting, according to Octavia Nasr, CNN senior editor for Arab affairs, who reviewed the recording. The voice urges residents of the region to stand up for themselves.
The 52-year-old al-Zawahiri, an Egyptian national, is considered to be Osama bin Laden's closest adviser and is viewed by many analysts as the operational brains behind the al Qaeda terror network.
Al-Zawahiri is one of the most-wanted terrorists in the United States. He was indicted along with bin Laden for his alleged role as mastermind of the 1998 bombings of the U.S. embassies in Kenya and Tanzania that killed 224 people.
U.S. government sources also believe he played a significant role in the September 11, 2001, attacks.
CNN's Octavia Nasr contributed to this report.