"The American defeat in Iraq and Afghanistan has become just a question of time, God willing" he said in a videotape aired on Aljazeera television Thursday.

Al-Zawahri, the right-hand man of al-Qaeda leader Osama bin Laden, wore a white turban and had a machine gun at his side in the videotape, aired two days before the third anniversary of the September 11 attacks on the US.

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"In the two countries, (Iraq and Afghanistan) the Americans are between two fires: if they remain there they will bleed to death, and if they withdraw they will have lost everything, " he said. The Mujahidin are in a strong position in Afghanistan and have turned US plans in Iraq "head over heels", he said.

In Afghanistan, the Mujahideen have driven US forces to "hide in their trenches", he said. "East and south Afghanistan have become an open arena for the Mujahidin. The enemy is limited to the capitals."

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"The Americans are hiding in their trenches and refuse to come out to face the Mujahideen, as the Mujahideen shell and fire on them, and cut roads off around them. Their defence is only to bomb by air, wasting US money as they kick up dust."

"In Kabul, the Americans and peacekeeping forces are hiding from the shells of the Mujahideen and expect martyrdom attacks at every moment," he said.

Al-Zawahri was last heard in March when Aljazeera aired a recorded message in which he called on Pakistanis to overthrow US-allied Pervez Musharraf government, Al Jazeera said. Al-Zawahri and Bin Laden last appeared in a videotape aired on Aljazeera in September 2003 in which the two were shown walking in a mountainous area together.

Complete coverage: The war in Iraq / America's war on terror