Al-Zawahri, who appeared sitting on the ground and in front of a brown background, said the U.S. military prison in Guantanamo Bay, Cuba, "explains the truth about reforms and democracy that America is allegedly trying to impose in our countries."
"Reform is based on American detention camps like Bagram, Kandahar, Guantanamo and Abu Ghraib, it will be based on cluster bombs and imposition of people like Karzai and Allawi," he said, referring to Afghan President Hamid Karzai and Interim Iraqi Prime Minister Ayad Allawi.
"Real security is based on mutual cooperation with the Islamic nation on the basis of mutual respect and the stopping of aggression."
Al-Jazeera reported that the excerpt was part of a longer videotape, but it did not indicate the length of the entire tape. The station did not say if it would air the rest of the video.
In Washington, the CIA said it was looking at the tape in an effort to determine its authenticity.
Al-Zawahri was wearing a clean and well-pressed white and brown robe and traditional headdress in the tape. A Kalashnikov assault rifle was leaning behind him against the backdrop.
"Real security is based on mutual cooperation with the Islamic nation on the basis of mutual respect and the stopping of aggression," al-Zawahri said in the tape.
He warned that "the new crusade is doomed to fail" and said it would result in "tens of thousands of fallen victims and the destruction of your economy."
"If you, the Western nations, think that these cardboard governments can protect you, you are wrong," he said in the tape about governments in the Middle East. "Your real security is through cooperation with the Islamic Nation."
Like al Qaeda chief Osama bin Laden, the Egyptian al-Zawahri is believed to be on the run in the mountains along the Afghan-Pakistani border.
But Pakistani officials have said there is no evidence either man is in their territory, and both Pakistani and American generals agree the trail has gone cold more than three years after the Sept. 11 attacks.