The twin towers on Sept. 11, 2001 (AP photo)

Despite his silence, Osama bin Laden has been planning a huge attack that would dwarf the suicide strikes on New York and Washington in 2001.

The U.S. intelligence community has assessed that bin Laden has benefited from a secure haven in Pakistan that allows him to plan a major attack on the United States. The community believes the absence of a major al Qaeda strike has stemmed from a lack of capability rather than will.

"Bin Laden has been very clear that each of al Qaeda's attacks on America will be greater than the last, and I think the only reason we haven't seen an attack so far is that he doesn't have that attack prepared," former CIA veteran Michael Scheuer said. "But when he does, he will use it. And try to get us out of the way, which of course is his main goal."

Officials said over the last six months, bin Laden's confidence has increased as he remains protected by tribes along the Afghan-Pakistan border. They said bin Laden has allowed his No. 2, Ayman Zawahiri, to issue frequent statements while the al Qaeda chief plans mass-casualty attacks on Europe and the United States.

Outgoing National Intelligence Director John Negroponte told the Senate Select Intelligence Committee on Jan. 11 that al Qaeda was believed to be plotting a conventional explosive attack against the United States. Mr. Negroponte said bin Laden and the rest of the al Qaeda leadership have been communicating to affiliates throughout the Middle East, North Africa and Europe.

"Pakistan is our partner in the war on terror and has captured several al Qaeda leaders," Mr. Negroponte said. "However, it is also a major source of Islamic extremism. Eliminating the safe haven that the Taliban and other extremists have found in Pakistan's tribal areas is not sufficient to end the insurgency in Afghanistan, but it is necessary."

Al Qaeda's increasing capabilities have resulted in networks in such countries as Algeria, Iraq, Lebanon, Somalia and Yemen. Officials said last week's U.S. air strikes on al Qaeda’s strongholds in southern Somalia were meant to prevent an Islamic takeover that could threaten U.S. interests throughout Africa.

Officials said the al Qaeda leadership was planning attacks with networks that have a presence in the West, particularly Britain and Canada.

They said al Qaeda has also established links with organizations that already have a presence in the United States, such as Hamas.

FBI Director Robert Mueller said al Qaeda has been regenerated and could count on a cadre of seasoned veterans for terrorist strikes on aviation, energy, mass transit as well as government buildings. He said al Qaeda could repeat the 9/11 strikes with operatives who enter the United States, particularly from Britain.

"It is also possible however, that al Qaeda's strategy for attacking the U.S. homeland includes using the UK as a stepping stone for al Qaeda operatives to enter the United States. We are working closely with our partners in the United Kingdom to counter this possible threat and to identify any U.S. connections to the UK networks currently being monitored."