In a tape released Tuesday, a voice believed to be Bin Laden's called for attacks on Americans if the United States goes to war with Iraq.
Addressing the Armed Services Committee, Tenet said bin Laden messages in October and November were followed by attacks: the nightclub bombing in Bali in the first case, the attack on a hotel in Kenya in the latter.
The spy agency chief, in his second straight day of testimony to Congress, again warned that another terrorist attack might be imminent.
"(Intelligence) points to plots timed to occur at the end of the Hajj…later this week and it points to plots that use radiological dispersal devices, poisons and chemicals," he said. "The information points to plots on two fronts: the United States and the Arabian peninsula."
"If given the choice, al Qaeda terrorists will choose attacks that achieve multiple objectives, striking prominent landmarks, inflicting mass casualties, causing economic disruption and rallying support through shows of strength," the CIA director said. "The bottom line here, Mr. Chairman, is that al Qaeda is living in the expectation of resuming the offensive."
Around the country, there was apprehension about a possible strike days after the White House upped the nation's terror alert status to "high."
New York City police officers stopped and searched a van on the Whitestone Bridge, which joins Queens and Brooklyn, before letting the vehicle pass. Authorities at Boston's Logan Airport evacuated a small plane because of a suspicious package. A defense official confirmed for CBS News.com that air defense batteries have been deployed in Washington "within the past few days."
The Homeland Security Department has advised citizens to stock up on supplies, such as duct tape to seal rooms, in case of an attack. But Senate Democratic Leader Tom Daschle of South Dakota criticized the administration's response.
"I hope the administration will get beyond the duct tape and get to the real serious issues that we've got to face in making a coordinated effort more of a reality," he said. "Before these suggestions are made, they need to think through what exactly the message is."
Tenet's visit to Capitol Hill was his second in as many days. In remarks to the Senate Intelligence Committee on Tuesday, the CIA director said intelligence information suggests the possible al Qaeda attack may involve a "dirty bomb" — a weapon that spreads radioactive material over a wide area — or chemical or poison weapons.
The information pointing to imminent attacks was gathered in the United States and overseas, said FBI Director Robert Mueller, who joined Tenet on the hill Tuesday.
Mueller and Tenet said the U.S. government has no specific information pointing conclusively to where, when or how terrorists would strike.
"The intelligence is not idle chatter on the part of terrorists and their associates," Tenet said Tuesday.
Mueller and Tenet said al Qaeda is damaged but still dangerous. Mueller called it "clearly the most urgent threat to U.S. interests." It has a strong presence in Pakistan and Afghanistan and is developing a presence in Iran and Iraq, Tenet said.
The FBI suspects there are "several hundred" Muslim extremists in this country who focus mainly on fund raising, recruitment and training, Mueller said. But he said the greatest threat to Americans at home are "al Qaeda cells in the United States that we have not identified."
Some of these cells have probably been in the United States since well before the Sept. 11 attacks, he said.
Echoing the White House and State Department, Tenet said he was worried about Iraq's alleged effort to obtain weapons of mass destruction and supposed ties to terrorism.
Maj. Barry Venables, a spokesman for NORAD, said a "multi-layered air defense" network had been put into action in the past few days, involving ground-based defense systems, fighter jets and helicopters.