The Pentagon says al-Qaeda would fragment if Osama bin Laden were killed.
The US military believes the surviving lieutenants of the terrorist organisation would take over sections of the network to pursue their own goals.
At least six leaders are dead and a few more are in US custody, but more than a dozen remain at large.
Without bin Laden, the surviving leaders would have difficulty keeping the group together, Vice Adml Thomas Wilson, director of the Defence Intelligence Agency, told the Senate Intelligence Committee.
In a statement, he said: "There is no identified successor capable of rallying so many divergent nationalities, interests, and groups to create the kind of cohesion he fostered among Sunni Islamic extremists around the world".
But Vice Adml Wilson said that without bin Laden, al-Qaeda could "splinter into a number of loosely affiliated groups, united by a common cause and sharing common operatives".
Previously, US officials have identified bin Laden's top two deputies, Egyptians Ayman al-Zawahri and Mohammed Atef, as potential successors.
Atef, a military commander, was killed by a US airstrike in November near Kabul. Al-Zawahri, a doctor and bin Laden's spiritual adviser, remains on the run along with bin Laden.
Abu Zubaydah, an international terrorist operations chief, and Saif al-Adil, the head of bin Laden's security detail, are also identified as possible successors.
PA
