In an audio message released two days after the 12th anniversary of the attacks, Ayman al-Zawahri claims America is not a "mythical power" and that the mujahedeen -- Islamic holy warriors -- can defeat it with attacks "on its own soil."
He says al-Qaida fighters should stage small attacks or a "big strike," similar to the Sept. 11 attacks in New York and Washington, leaving America in "a state of tension" about when and where the next hit would come.
The message's authenticity could not be independently confirmed. It was posted on a militant website commonly used by al-Qaida.
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