In an audio message recently released, Zawahiri (left) laid out a plan of attack, saying he wanted a "few of the brothers" to commit small-scale strikes to trigger big spending by Washington on security, while awaiting the opportunity for a major onslaught later.
"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," he said.
Keeping America in such a state of tension and anticipation only required a few disparate attacks "here and there".
He said: "As we defeated it in the gang warfare in Somalia, Yemen, Iraq and Afghanistan, so we should follow it with ...war on its own land. These disparate strikes can be done by one brother or a few of the brothers."
At the same time, Muslims should seize any opportunity to land "a large strike" on the United States, even if this took years of patience, he said in the audio speech, which was broadcast on an Internet forum normally used by jihadist groups and lasted 72 minutes.
In his audio speech, Zawahri said Muslims should refuse to buy goods from America and its allies, as such spending only helped to fund US military action in Muslim lands. He added that Muslims should abandon the US dollar and replace it with the currency of nations that did not attack Muslims.
"The Boston incident confirms to the Americans ... that they are not facing individuals, organizations or groups, but they are facing an uprising Ummah (Muslim community), that rose in jihad to defend its soul, dignity and capabilities."
"What the American regime refuses to admit is that al Qaeda is a message before it was an organization," he said.