File photo of al-Qaeda leader Ayman al-Zawahri. AFP | Getty Images

Al-Qaeda's leader on Friday marked the anniversary of the Sept.11, 2001, attacks by calling on Muslims to strike inside the United States, with big attacks or small, using any opportunity they can to "bleed" America financially. In an audio message released two days after the 12th anniversary of the attacks, Ayman al-Zawahri said America is not a "mythic power" and that the mujahedeen, Islamic holy warriors can defeat it with attacks "on its own soil." Al-Zawahri, the successor to Osama bin Laden, used the anniversary to argue that the United States can be defeated by targeting its economy. At the same time, he also addressed the ongoing upheaval in the Arab world. Pointing to a power struggle going on within the rebellion against Syria's regime, he warned that jihadi fighters in that country's civil war should not "compromise" with more secular or moderate rebel factions ,who he said would eventually turn against the al-Qaeda-linked radicals. The message's authenticity could not be independently confirmed. It was posted on a militant website commonly used by al-Qaeda. (Read more: Kerry calls Syria talks constructive)

Al-Zawahri, who is believed to be hiding in the Pakistan-Afghanistan border regions, said al-Qaeda sympathizers should stage small attacks or a"big strike" against the United States, 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. Small attacks could be done by only a few or even just one person, while at the same time "we must watch and wait to seize any opportunity to direct a large strike on (America), even if that takes years of patience to do it," he said. "We should bleed America economically by motivating it to continue its huge expenditure on its security as America's weak point is its economy,which already has begun stumbling because of the military and security expenditure," he said. "America is not a mythic power and the Americans,after all, are humans who can be defeated, felled and punished." (Read more: )

He urged the Islamic world to "abandon the dollar and replace it with a currency of other countries that are not taking part in the aggression against us." On Syria's civil war, al-Zawahri addressed al-Qaeda-linked jihadis including many foreign fighters who have taken an increasingly prominent role in the fight against President Bashar Assad's regime. Their rise has caused tensions with more moderate Syrian rebel factions,even escalating to violence and turf battles. The United States and its allies have said they want to build up moderate rebel factions to reduce jihadi influence. America wants to use "the Muslim people as a means to topple the pro-Iran Baathist regime and install a secular government and peaceful to Israel," al-Zawahri said. It "will try to push the mujahedeen to compromise with the secular factions and the enemies of Islam." (Read more: Syria focus will fan flames of September volatility)