CIA Director George Tenet issued a new warning that Osama bin Laden's al Qaeda network, blamed for the Sept. 11, 2001, attacks on the United States, was as serious a threat as ever despite having been dealt several blows in the war on terrorism.

"Intelligence information tells us the al Qaeda leadership has been rattled by recent losses and is taking more precautions. But let's be clear, there is no letup in the threat at this moment," Tenet said Wednesday in a speech to an awards ceremony held by the Nixon Center, a Washington think tank.

"Intelligence clearly shows al Qaeda is still preparing terrorist attacks," Tenet said. "Indeed, every al Qaeda operations officer and facilitator that we have so far captured was in the midst of preparing attacks when they were captured."

Several senior al Qaeda members have been captured or killed since the United States launched its war on terrorism in Afghanistan in October, but bin Laden is believed to still be alive.

Tenet said al Qaeda tapes released about the same time as recent attacks in Bali, Kuwait and the Kenyan city of Mombasa were designed to bolster morale among al Qaeda recruits.

"We need to show al Qaeda's potential recruits that al Qaeda is failing in every possible respect," he said. "If we can't take them off the board, we have to keep them on the run."

Al Qaeda is suspected in the Oct. 12 blasts at a Bali nightclub that killed at least 191 people and in an attack earlier in the month that killed a U.S. Marine in Kuwait.

Al Qaeda claimed responsibility for a suicide bombing at a hotel in Mombasa on Nov. 28 that killed 13 Kenyans and three Israelis. The network also failed in an attempt to shoot down with missiles an Israeli airliner.

Al Qaeda member Suleiman Abu Ghaith vowed in an audio statement released by an Islamic Web site that there would be "bigger and more lethal operations" to come.

"They would be foolish to make so bold a threat unless they were confident that some impending operation had a high probability of success," Tenet said. "We would be foolish to take these threats with anything other than the utmost seriousness."

Defending his agency's performance in the war against al Qaeda, Tenet said the CIA had been hitting the network's infrastructure well before Sept. 11, 2001.

Earlier Wednesday, Tenet and his agency were criticized after the release of a report by a House-Senate Intelligence panel that examined intelligence community failures before the Sept. 11 attacks.

Sen. Richard C. Shelby of Alabama, the Senate panel's top Republican and a persistent critic of Tenet, said, "There have been more massive failures of intelligence on his watch as director of CIA than any director in the history of the agency."