WASHINGTON (AFP) – US Defense Secretary Robert Gates said Sunday that Al-Qaeda had been seriously degraded and could split into a set of regional terror groups now that Osama bin Laden was gone.

"First of all, they have been significantly weakened. There's just no two ways about it," Gates told CNN's "State of the Union" program, explaining that bin Laden was not the only Al-Qaeda figure to have been killed recently.

"We have taken a real toll on them over the last, particularly the last two years," he said.

Al-Qaeda on Thursday named long-time number two Ayman al-Zawahiri as its new leader after bin Laden was killed by US commandos in the dead of night in a May 2 raid on his hideout in Pakistan.

Zawahiri has been portrayed by US officials as a pale imitation of bin Laden, someone, they say, who lacks his predecessor's charisma and leadership skills and is also a divisive figure who could fracture Al-Qaeda.

"The question is whether Zawahiri, the new leader taking bin Laden's place, can hold these groups together in some kind of a cohesive movement, or whether it begins to splinter, and they become essentially regional terrorist groups that are more focused on regional targets. And we just don't know that yet," Gates said.

Like his slain Saudi-born co-conspirator, Zawahiri, a 59-year-old Egyptian, has been in hiding since the United States declared its war on terror after the September 11, 2001 attacks and is widely believed to be in Pakistan.

Gates, 67, leaves his post at the end of the month. His designated replacement is the current CIA director, Leon Panetta, who will soon turn 73.