The United states has vowed to hunt down and kill new al-Qaeda boss Ayman al-Zawahiri.

"He (Zawahiri) and his organisation still threaten us. As we did both seek to capture and kill and succeed in killing bin Laden, we certainly do or will do the same thing with Zawahiri," Admiral Mike Mullen, Chairman of the US Joint Chiefs of Staff, told reporters at a Pentagon news conference.

Born in Egypt, al-Zawahiri was the obvious successor to Osama Bin Laden and is said to have been the mastermind behind many of the terrorist acts attributed to Al Qaeda.

Earlier this year the US finally tracked down and killed al-Zawahiri’s predecessor Osama Bin Laden in Pakistan. Bin Laden was responsible for orchestrating 9/11 terrorist attacks which killed more than 3000 people.

In a press conference outgoing Secretary of Defense, Robert Gates said al-Zawahiri may struggle to fill Bin Laden’s shoes.

"Bin Laden has been the leader of al-Qaeda, essentially since its inception,” he said.

“In that particular context, he had a peculiar charisma that I think Zawahiri does not have. I think he was much more operationally engaged than we have the sense Zawahiri has been," he said.

"We should be mindful that this announcement by al-Qaeda reminds us that, despite having suffered a huge loss with the killing of bin Laden, and a number of others, al-Qaeda seeks to perpetuate itself, seeks to find replacements for those who have been killed, and remains committed to the agenda that bin Laden put before them," Gates said.


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