Ayman al-Zawahiri, the second-in-command of the al Qaeda, may succeed Osama Bin Laden, but the Egyptian-born doctor may have difficulties in maintaining loyalties of large followers of the slain terrorist.
Al-Zawahiri, who was almost a shadow of bin Laden, is also in hiding ever since the US declared its war on terrorism in 2001 after the 9/11 attacks in New York and Washington.
A senior US official said al-Zawahiri is likely to succeed Osama bin Laden, but added that he lacks the charisma and is not as respected within the organisation.
He is also on US' most-wanted list and was indicted in the US for the bombing of two US embassies in Africa in 1998.
US official say that the terror scene has become more complicated with powerful groups like Lashkar-e-Tayyaba and Jaish-e-Mohammed gaining a foothold in the tribal areas.
"As the only al Qaeda leader whose authority was universally respected, he also maintained his cohesion, and his likely successor, Ayman al-Zawahiri, is far less charismatic and not as well respected within the organisation, according to comments from several captured al Qaeda leaders. He probably will have difficulty maintaining the loyalty of bin Laden's largely Gulf Arab followers," a senior administration official said.
Officials said there is no doubt that the death of Osama bin Laden marks the single greatest victory in the US-led campaign to disrupt, dismantle, and defeat al Qaeda.
Bin Laden was al Qaeda's only commander in its 22-year history, and largely responsible for its mystique, its attraction among violent jihadists, and its focus on America as a terror target.
Although al Qaeda may not fragment immediately, the loss of bin Laden puts the group on a path of decline that will be difficult to reverse, the official noted.