Zawahiri, in an audio message addressed to Somali militant group al-Shabaab, said U.S. influence in the Middle East was waning now that it's military engagements there have ended.
"They were defeated in Iraq and they are withdrawing from Afghanistan and their ambassador in Benghazi was killed and the flags of their embassies were lowered in Cairo and Sanaa (Yemen)," a translation of the message published by the online Long War Journal read.
U.S. Secretary of State Hillary Clinton ordered the FBI to investigate the Sept. 11 attack in Libya. Shortly afterward, she suggested al-Qaida in the Islamic Maghreb was likely behind the raid. U.S. Secretary of Defense Leon Panetta said it was "pretty clear" that the attack in Benghazi was an act of terrorism.
"Their awe is lost and their might is gone and they don't dare to carry out a new campaign like their past ones in Iraq and Afghanistan," said Zawahiri.
U.S. officials have said they were shifting their focus to the Asia-Pacific. A September report from U.S. policy center Rand Corp. warns that a "fourth wave" of al-Qaida is spreading to new areas of the Middle East and North Africa as the U.S. strategic focus moves east.