U.S. intelligence officials, increasingly confident that al Qaeda leader Osama bin Laden is the speaker on a new audiotape released this week, said yesterday that the message was part of a disturbing pattern indicating that terrorist groups may be planning a new wave of attacks on Western targets.

Even before the purported bin Laden tape surfaced on the al-Jazeera satellite network on Tuesday, the CIA, FBI and National Security Agency had detected a significant spike in intelligence "chatter" over the previous 10 days that strongly indicated new assaults are being planned, officials in U.S. intelligence agencies said.

The amount of alarming information was approaching the volume seen in the weeks before the Sept. 11, 2001, attacks in Washington and New York, and again in the middle of last month following a wave of attacks on overseas targets, some sources said. The emergence of the new tape -- on which bin Laden praises the recent terror attacks and threatens more if the United States goes to war against Iraq -- only heightens the sense of alarm, the officials said.

The tape also comes as the United States moves toward a confrontation with Iraq, and serves as an unwelcome reminder that the Bush administration still has not finished its battle with the al Qaeda network. Unlike an Oct. 6 audiotape attributed to bin Laden, which was inconclusive as to when it was recorded, this week's tape refers to the string of attacks overseas, including the Oct. 12 bombing outside a Bali nightclub and the deadly standoff with Chechen gunmen that ended in Moscow on Oct. 26.

President Bush, who last year said he was determined to get bin Laden "dead or alive," bristled yesterday when reporters asked whether the United States should have already brought him to justice.

"We're making great progress in the war on terror. Slowly but surely we are dismantling the terrorist network," the president said. "We're on a manhunt. And we're not quitting. Slowly but surely, we're achieving our objective."

Government language specialists who have listened to bin Laden before believe he is the speaker on the al-Jazeera tape, according to senior administration officials. The National Security Council also circulated a classified e-mail yesterday concluding that the voice was confirmed as coming from bin Laden, two sources said.

Some senior officials raised doubts about the tape's authenticity, saying technicians have been unable to match bin Laden's voice using special equipment. Additional questions are being raised by some analysts who believe that parts of what the speaker said do not fit bin Laden's previous patterns. Other officials said the technical problem may be due to the quality of the recording, which they said was poor and may have been made over a satellite or cellular phone.

Based on the tape and other evidence, U.S. analysts believe that bin Laden is probably in very poor health and unable to travel extensively, meaning he has either found a place where he can stay for extended periods or limits his travel to a particular region, according to two senior U.S. officials. The fact that bin Laden sent an audiotape rather than a videocassette may indicate he is in poor physical shape and does not want to be seen by his followers and the world as weakened, the officials said.

Regardless of the tape's origin, intelligence analysts said they are worried by the timing of its release and by the nature of its message.

In congressional testimony last month, CIA Director George J. Tenet warned that recent attacks in Yemen, Kuwait and Bali signaled an escalation in terrorist activity, which he characterized "as bad as it was last summer" before the airliner hijacking assaults on the World Trade Center and the Pentagon.

The volume of threat information waned in the weeks following Tenet's Oct. 17 testimony, only to begin rising again over the last week to 10 days, sources said. The magnitude is again approaching pre-Sept.11 levels, these sources said.

"That threat environment level was high then, and it has not lessened," a senior administration official said yesterday. Factors contributing to the increase could include the threat of war against Iraq or the celebration of the Muslim holy month of Ramadan, which began this week.

On the tape, bin Laden lauded the terrorist incidents in Bali, Kuwait, Yemen and Moscow as justifiable actions "carried out by the zealous sons of Islam in defense of their religion," and warned, "As you kill, you get killed, and as you bomb, you get bombed."

Bruce Hoffman, a terrorism expert who heads the Rand Corp.'s office here, said the tape "could mean that something has been set in motion."

"Bin Laden's appearances have always been carefully orchestrated, and unfortunately they've often presaged a major al Qaeda attack or development," Hoffman said.

The tape is also notable for its explicit references to Islamic countries "allied with the tyrannical U.S. government," and likens the suffering of Iraqis to the plight of Palestinians. Yet the speaker makes no mention of two other themes prominent in bin Laden's past oratory: complaints about the U.S. military presence in Saudi Arabia and the need to eliminate secular leaders, like Saddam Hussein, from Islamic governments.

Though bin Laden in the past has sympathized with Iraq over the U.S.-led economic embargo, saying it has cost the lives of Iraqi children, he has never put Hussein's survival as a focus of his cause.

Richard C. Shelby (Ala.), ranking Republican on the Senate intelligence committee, said the tape should prompt a redoubling of efforts to find bin Laden. As the search for bin Laden remained inconclusive, and as talk of war with Iraq took center stage within the Bush administration, the Pentagon reduced the number of Special Forces and others assigned to find the Saudi-born militant.

Sen. John F. Kerry (D-Mass.), a likely presidential candidate, said the tape "certainly underscores the incompleteness of that task." Alluding to criticism from some Democrats that Bush is able to focus on only one task at a time, Kerry said the bin Laden tape "certainly heightens suspicions that they are overfocused on one [Iraq] and made mistakes on the other."

"This is a very stark, bleak reminder of what is yet to do out there," said Sen. Chuck Hagel (R-Neb.). "We made a statement a year ago that we would find him and destroy him, and it is very difficult to do that."

Juliette Kayyem, a terrorism expert at Harvard University's Kennedy School of Government, called the tape a "symbolic setback" for Bush.

"To the extent that success in the war on terrorism is bent on getting and ending the life of bin Laden, this is certainly a challenge for the administration," Kayyem said. "They have tried to distance themselves from bin Laden, but he keeps reappearing."

Within the administration, however, officials insisted that the reemergence of bin Laden had not caused overwhelming concern. They said the administration's course is set, both on Iraq and in the broader war on terrorism. "We're not spending a lot of time changing our views and goals," said a senior administration official. "We can do more than one thing at a time."

Some officials, eager to find links between Hussein and al Qaeda, have begun to make the case that the audiotape could provide evidence of collusion between Hussein and bin Laden, largely because of the timing of the tape's release on the eve of resumed United Nations weapons inspections in Iraq. The CIA and other intelligence agencies have found scant evidence of such a link.

Richard A. Boucher, the State Department spokesman, said he made a list of all the nations that bin Laden threatened in the tape, ticking off Britain, France, Italy, Canada, Germany, Australia, Indonesia, Tunisia, Kuwait, Jordan, Russia and Pakistan.

"The global effort against terrorism continues and will not diminish one way or the other," he said. "It's important that we all band together."

Staff writers Walter Pincus, Vernon Loeb, Mike Allen, Douglas Farah and Dana Priest in Boston contributed to this report.

In congressional testimony last month, CIA Director George J. Tenet said attacks in Yemen, Kuwait and Bali signaled escalation of terrorist activity.