The Al Qaeda terrorist organization would fragment if Usama bin Laden were killed, with surviving lieutenants taking over sections of the network to pursue their own goals, a top Pentagon intelligence official says. 

At least six leaders are dead, and a few more are in U.S. custody, but more than a dozen key lieutenants remain at large. So, for the moment, intelligence officials say Al Qaeda can reconstitute itself. 

Absent bin Laden, the surviving leaders would have difficulty keeping the terrorist group together, Vice Adm. Thomas R. Wilson, director of the Defense Intelligence Agency, told the Senate Intelligence Committee on Wednesday. 

"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," Wilson said in written testimony. 

Previously, U.S. 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 U.S. airstrike in November near Kabul. Al-Zawahri, a doctor and bin Laden's spiritual adviser, remains at large along with the terrorist leader himself. 

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. 

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." 

A splintered Al Qaeda probably wouldn't have the wherewithal to pull off the complex, simultaneous operations Al Qaeda is known for, but they would remain a threat, Wilson said. 

"The group has suffered a loss of prestige, institutional memory, contacts and financial assets that will ultimately degrade its effectiveness," Wilson said of Al Qaeda. "Many key officials and operatives remain, and new personalities have already begun to emerge." 

After Atef, chief among those U.S. officials say are dead: 

— Abu Hafs the Mauritanian, who provided some of the scholarly justification for Al Qaeda's terrorist attacks. 

— Abu Jafar al-Jaziri and Abu Salah al-Yemeni, identified as senior logistics coordinators. 

— Tariq Anwar al-Sayyid Ahmad and Muhammad Salah, two Egyptians involved in executing terrorist attacks. 

There have been unconfirmed reports that Mohammad Omar Abdel-Rahman, son of a blind Egyptian sheik convicted of leading a bombing conspiracy in New York in the mid-1990s, was killed, but U.S. authorities believe he remains at large. 

The captured include: 

— Ibn Al-Shaykh al-Libi and Abd al-Hadi al-Iraqi, who commanded some of bin Laden's Afghan training camps. 

— Ahmed Omar Abdel-Rahman, another son of the blind sheik, who was also reportedly captured by anti-Taliban forces. He is considered a midlevel Al Qaeda official and a liaison to his father's Egypt-based terrorist organization, al-Gamaa al-Islamiya. His status is unclear. 

The United States is still gunning for those still at large. On Monday, the CIA fired missiles from at least one Predator drone at a suspected Al Qaeda senior official. At least one person targeted was killed, but his identity is unclear, a U.S. official said. An Afghan leader put the death toll at seven suspected Al Qaeda members. 

CIA Director George J. Tenet told the Senate Intelligence Committee on Wednesday, "Al Qaeda leaders still at large are working to reconstitute the organization and resume its terrorist operations." 

U.S. intelligence is tracking developments in a number of places where Al Qaeda leaders fleeing Afghanistan may try to land. These include Somalia, Sudan, Chechnya, Lebanon, Palestinian areas, Yemen and elsewhere. So far, officials haven't seen any mass movement of Al Qaeda members to a particular place. 

One reason bin Laden remained popular among extremists is that he preaches a doctrine that spans all of Sunni Islam, and he doesn't limit his philosophy to the Arab world, officials and experts say. 

His ranks include Muslims from southeast Asia, Europe and non-Arab Africa, but it is unclear if any of his chief lieutenants would maintain his international, pan-Sunni vision.