CIA Director George Tenet told the Senate Intelligence Committee in a briefing that information pointing at those targets led to last week's raising of the national terror alert level to "orange," the second highest level of five. The information came from "multiple sources with strong Al Qaeda ties," Tenet said, without providing details.

"The intelligence is not idle chatter on the part of terrorists and their associates," Tenet said Tuesday. "It is the most specific we have seen, and it is consistent with both our knowledge of Al Qaeda's doctrine and our knowledge of plots this network -- and particularly its senior leadership -- has been working on for years."

The information pointing to imminent attacks was gathered in the United States and overseas, said FBI Director Robert Mueller, who joined Tenet and other intelligence chiefs to brief the committee in an annual public session on threats to national security.

The CIA director said the information suggests the attack may involve a "dirty bomb" -- a weapon that spreads radioactive material over a wide area -- or chemical or poison weapons. Officials last week worried the attack could be timed to coincide with the hajj, a Muslim holy period this week.

Mueller and Tenet said the U.S. government has no specific information pointing conclusively to where, when or how terrorists would strike. They said raising the national alert level -- and taking security measures at government and business centers -- makes it more difficult for the terrorists to carry out an attack.

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.

"The enemies we face are resourceful, merciless and fanatically committed to inflicting massive damage on our homeland, which they regard as a bastion of evil," Mueller said.

Tenet had little information Tuesday morning on a new audio message attributed to Usama bin Laden, which aired later in the day on the Arab television station Al-Jazeera. Some previous recordings of the Al Qaeda chief have served as preludes to terrorist attacks.

The CIA chief also repeated many of Secretary of State Colin Powell's statements last week to the United Nations regarding Iraq's efforts to acquire chemical, biological and nuclear weapons, and linking Al Qaeda supporters to the Iraqi government. Tenet said the key link between Baghdad and Al Qaeda is Abu Musab Zarqawi, a senior associate of bin Laden.

He said about two dozen of Zarqawi's followers remain in Baghdad, where Zarqawi spent two months last summer. All are members of Egyptian Islamic Jihad, a terrorist group that has merged with Al Qaeda, Tenet said. But he said he has no evidence suggesting Iraq has any operational control over Zarqawi's group or Al Qaeda.

Echoing Bush administration policy-makers, Tenet and the other intelligence chiefs offered little hope that U.N. inspections would prompt Iraq to disarm, saying Saddam is intent upon and capable of circumventing the inspections.

Tenet also said U.S. intelligence has given U.N. inspectors all of its information on what it believed were Iraqi weapons sites. CIA officials declined to say how many of those sites the inspectors have visited.

Vice Adm. Lowell E. Jacoby, director of the Defense Intelligence Agency, predicted Saddam would lash out in many directions if attacked.

"I expect him to pre-emptively attack the Kurds in the north, conduct missile and terrorist attacks against Israel and U.S. regional or worldwide interests -- perhaps using WMD (weapons of mass destruction) and the regime's links to Al Qaeda," Jacoby said in prepared remarks. "Saddam is likely to employ a scorched-earth strategy. ... We should expect him to use WMD on his own people."

The Associated Press contributed to this report.

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