Wearing a white turban with a rifle leaning behind him, the bespectacled Egyptian surgeon said "southern and eastern Afghanistan have completely become an open field for the mujahedeen."
Southern and eastern Afghanistan have been wracked by the fiercest resistance to U.S. military forces and there have been frequent attacks on Afghan election workers preparing for an Oct. 9 presidential vote.
However, no Afghan provincial government is considered in jeopardy of falling and Afghan and U.S. forces have largely controlled the country.
"The Americans are huddled in their trenches, refusing to come out to confront the holy warriors despite the holy warriors' provoking them by shelling, shooting and cutting the routes around them and their defense concentrates on strikes from the air which wastes America's money in kicking up dust," al-Zawahri said in brief excerpts of the tape aired by the Qatar-based station.
It's not so much what al-Zawahri had to say, as the fact that he said anything at all that concerns U.S. officials, reports CBS News Correspondent Jim Stewart. That's because in the past, when al Qaeda leaders spoke out, terror attacks followed.
In the spring, 16 days after an al-Zawahri message, four trains were bombed in Madrid. Prior to the Madrid bombs, two Thai policemen died from an al Qaeda bomb just 24 hours after Bin Laden spoke.
U.S. officials are studying the tape, but say it's too soon to say if the man and the voice match al-Zawahri. They caution that not every tape is followed by an attack, but believe it is no coincidence that this tape was released just before the third anniversary of the Sept. 11 terror attacks. It could be a mocking reminder that the men who planned it are still free, reports Stewart.
The last statement purported to have been made by al-Zawahri surfaced June 11, when an audiotape believed to be that of the al Qaeda chief was broadcast by Al-Arabiya TV, on which the speaker said a U.S. plan for reform in the Middle East was really a bid to replace Arab leaders.
Al-Jazeera said it had received the latest al-Zawahri tape exclusively, but it was not immediately clear how or when it received it.
The release of the tape comes two days before the third anniversary of the Sept. 11 attacks on the United States, which were blamed on al Qaeda. A U.S.-led coalition launched attacks on Afghanistan aimed at destroying al Qaeda camps and the Taliban government that had hosted bin Laden and his followers.
A day before the second anniversary of the attacks on New York and Washington D.C., al-Zawahri and bin Laden also appeared on another tape aired by Arab TV.
In the latest tape, al-Zawahri said the peacekeeping force and American troops in Kabul have been "burnt by the shells of the holy warriors and expect martyrdom operations all the time, with God's help."
Al-Jazeera's presenter, reading before airing excerpts from the videotape, quoted al-Zawahri as saying that if it was not for the assistance provided by the Pakistani army to American forces, the U.S.-led coalition would have been driven out of Afghanistan long ago.
Afghanistan President Hamid Karzai has said recently that he considers infighting among pro-government warlords a larger threat to the nation's stability than that posed by the remnants of the Taliban regime.