A former Egyptian doctor-turned-practitioner of Islamic holy war has emerged as the hands-on operational leader of the al Qaeda network, reducing Osama bin Laden to a figurehead role, a top US counterterrorism official said late Friday.
Cofer Black, a former chief al Qaeda hunter at the Central Intelligence Agency who now co-ordinates counter-terrorism activities at the State Department, warned that Ayman al-Zawahiri, a man associated with radical Islamic causes since the 1960s, "tends to be more operational than Osama bin Laden."
"I think Zawahiri represents more of a threat comparatively between the two men," Black told CNN television.
"Zawahiri is certainly in the field and operating, has lines of communication to his subordinates and is planning attacks as we speak."
He described bin Laden, the mastermind of the September 11, 2001, attacks, as a "figurehead" leader who was increasingly out of touch with his followers.
"He's very defensive. He knows we're after him. And he spends most of his time hiding from us," Black said of bin Laden.
The official went on to compare the al Qaeda founder to ousted Iraqi leader Saddam Hussein who had been hiding in an underground hole, completely cut off from the outside world, before US soldiers captured him last December.
Black did not say whether he believed al-Zawahiri and bin Laden were on the run separately or together. As many as 70 percent of al Qaeda's leadership have been captured or killed as a result of the US-led war on terror launched in the aftermath of September 11 in Afghanistan and other parts of the world, according to US intelligence officials.
More than 3,400 of the group's lower-ranking operatives and supporters have also been detained or otherwise neutralised, these officials insist.
But a report on world-wide terrorism patterns released by the State Department Thursday acknowledged that al Qaeda probably still has several thousand members and associates it can rely on.
Following the ouster of the Taleban regime in Afghanistan in 2001, and the closure of al Qaeda's training camps in the country, "al Qaeda has dispersed in small groups across South Asia, Southeast Asia, and the Middle East and probably will attempt to carry out future attacks against US interests," the report warned.
A scion of a prominent Egyptian intellectual family, 52-year-old al-Zawahiri studied to become a doctor but chose radical politics instead.
He cut his teeth with the fundamentalist group Muslim Brotherhood in the late 1960s before moving on to the more radical Egyptian Islamic Jihad and becoming one of its leaders.
Al-Zawahiri was caught in a dragnet sprung by Egyptian security services following the 1981 assassination of president Anwar Sadat, but was eventually release for lack of evidence against him.
He met bin Laden in Afghanistan, where he travelled in the 1980s to organise Islamic resistance to Soviet occupation and later co-authored with him a fatwa, or Islamic edict, calling for a world-wide Islamic front "against Jews and crusaders."
He has been indicted in the United States for his alleged role in the 1998 bombings of the US Embassies in Kenya and Tanzania that claimed the lives of 224 people.
In several audio tapes attributed to him and played on Middle Eastern television networks, al-Zawahiri called for new terror attacks against Americans and their allies.
Hopes for his capture went up briefly last March, when Pakistani reported their troops had likely surrounded an important al Qaeda figure in a walled-off complex in the Waziristan region.
Many believed that figure was al-Zawahiri, but the battle eventually yielded no significant al Qaeda leaders.