The speech was posted a day after America held ceremonies in honor of the nearly 3,000 people killed in the attacks of September 11, 2001.

"We should bleed America economically by provoking it to continue in its massive expenditure on its security, for the weak point of America is its economy, which has already begun to stagger due to the military and security expenditure," Zawahiri said according to the SITE translation.

"And keeping America in tension and anticipation only costs a few disparate attacks here and there, meaning as we defeated it in the gang warfare in Somalia, Yemen, Iraq and Afghanistan, so we should follow it with that war on its own land," he added.

Zawahiri went on to say that these strikes could be "done by one brother or a few of the brothers" and that it was worth waiting for the right moment in order to mount a large-scale attack.

"With these strikes, we must monitor and lie in wait and seize any opportunity to land a large strike on it, even if it takes years of patience for this," he said.

Zawahiri also referenced the twin bomb blasts at the Boston marathon in April that left three dead and scores wounded and maimed. (AFP)