Al-Qaeda’s ability to carry out large-scale complex strikes has “diminished” due to recent aggressive campaigns against it, but the terror network is trying to launch smaller attacks which are much more difficult to detect and thwart, the US Defence Department has said.

“…their (al-Qaeda and its extremist allies) ability to launch large-scale, complex attacks has clearly been diminished by the fact that we have taken the war as aggressively as we have to them,” Pentagon spokesman Geoff Morrell said.

“Now, has al-Qaeda and other associated terrorist groups, have they been able to disperse and crop up elsewhere? Yes. Are there problems that we need to deal with around the world? Yes,” he told MSNBC.

It is the belief of Pentagon and the Obama Administration that “we have been able to protect the homeland because we have been taking the fight to the terrorists where they operate, where they plan, where they try to hatch these attacks,” he said.

“By keeping them on their toes, unable to really launch large-scale, sophisticated, complex attacks which result in mass casualties, like we saw on 9/11, they are far diminished,” Morrell said in response to a question.

At the same time, the Pentagon spokesman conceded that these terrorist groups have been trying to carry out small-scale attacks.

“Well, listen, this is a very difficult situation that we are arriving at. Whereas we are having tremendous effect going after large-scale operations; so as a result, the terrorists are adapting, and they’re using more individuals to launch smaller attacks,” he said.

Such attacks, he observed, are much more difficult to detect and thwart, “because it’s not a number of people collaborating, increasing the chances that communications can be intercepted, individuals can make a mistake, the group’s activities can be uncovered by our detectives, by our intelligence apparatus”.

But a single person wishing to do harm is far more likely to get through the layers of protection, he argued, two weeks after Pakistani-American Faisal Shahzad allegedly tried to blow up a Nissan Pathfinder packed with explosives in the crowded Times Square.

“That is a reality we are confronted with; and yet, we are doing all we can to even prevent those. Individuals, as you saw with that vendor (in Times Square who alerted police about the parked vehicle with explosives inside) and others, can make a difference. That’s why we all have to be vigilant to protect the homeland against terrorists,” Morrell said.