The release of an audiotape purportedly made by Osama bin Laden's No. 2 agent is raising anxiety in US intelligence circles, and among the American public, about a possible imminent attack against the United States or its allies.
And perhaps with good reason.
Intelligence officials say that behind the latest broadcast - if it is authentic - are three possible motives:
• Code talk. As a possible exhortation to followers, it may deliver hidden instructions and spring plans into action. "It's never good news when [Ayman al-Zawahiri] speaks," says a senior intelligence official. "He spoke two days before the  east Africa bombings ... and he spoke about 20 days before the bombing of the USS Cole [in 2000]."
• Sowing fear. In addition to its operational function, the message may have psychological aims, making headlines and terrorizing the public. Already, those ends have been servedt: The tape came a day after President Bush had raised the national terror alert to "high," and it prompted the deployment of antiaircraft missiles around Washington, beefed-up searches at airports and borders, and an increased police and military presence.
• Recruiting new members. The public rhetoric often, as with this tape, exploits current conflicts and portrays Muslims as under attack. And the dispatches assure followers that Al Qaeda leaders take care of their own.
Though US officials are still trying to authenticate the tape, most say the voice and rhetoric match Dr. Zawahiri's.
"Al Qaeda is not only trying to beat the US," the senior intelligence official says. "It is trying to create a lasting legacy of international insurgencies by supporting conflicts in the Philippines, Kashmir, Pakistan, Chechnya, inside Iraq, Malaysia, Indonesia - everywhere on earth ... there is an Islamic insurgency."
Despite the inroads the US has made - destruction of Al Qaeda's home base and arrests or deaths of several members, some very high-ranking - the recent attacks in Saudi Arabia and Morocco show the group retains the ability for simultaneous strikes.
"We have disrupted Al Qaeda, and driven it out of its principal sanctuary in Afghan-istan," Samuel Berger, former national security adviser to President Clinton, said at a Monitor breakfast Thursday. "We have hardly destroyed it. It has obviously reconstituted in some ways. It never was a highly centralized operation in the first place."
Zawahiri's latest talk, which experts say is much like ones he's given in the past, addresses the Iraq war and the fact that the US now - arguably - occupies more Muslim countries than ever before.
"After dividing Iraq, Saudi Arabia, Iran, Syria, and Pakistan will come next," Zawahiri says. "What will be left around Israel is only dismembered semistates that are servants to the United States and Israel." He continues, "Be strong, O Muslims, and attack the missions of the United States, the UK, Australia, and Norway, and their interests, companies, and employees. Turn the ground beneath their feet into an inferno and kick them out of your countries."
Some experts say these entreaties are mainly for propaganda purposes - that Al Qaeda is in fact on the run and suffering from US-inflicted damage.
"It's designed to send a message to actual and would-be supporters throughout the world that the brains of Al Qaeda are still around and taking an active role," says Bruce Hoffman, an expert on terror at the RAND Corporation in Washington. On the other hand, he says, "We ignore their words at our own peril."
Zawahiri and Osama bin Laden, Hoffman and other experts say, have long used US actions in the world to portray their organization as a vanguard resisting an American-Zionist hegemonic force. Some 20 days prior to the October 2000 bombing of the USS Cole, in which 17 sailors died, Zawahiri appeared at a rally in Afghanistan, as reported in the Al Haya newspaper in London.
"Enough of words," said Zawahiri, Mr. bin Laden's likely successor. "It is time to take action against this iniquitous and faithless force [the US] which has spread its troops through Egypt, Yemen, and Saudi Arabia."
Zawahiri also spoke two days before the 1998 East Africa embassy bombings. On that occasion, the senior intelligence official says, Zawahiri took advantage of drawn-out planning stages for the attack, and sent a message to adherents.
"One of his fighters in an Albania cell had just been shot and killed by the police," the intelligence official says. "It was an announcement to his group that 'we will respond in kind with the only thing Americans understand.' "
A few days later, 302 people died in the embassy bombings, including 12 Americans. Some 5,000 were wounded.
Between bin Laden and Zawahiri, there have been scores of talks, interviews, and orders. The book "Through Our Enemies' Eyes," written by an anonymous intelligence officer, thoroughly explores the correspondence and its aftermath.
But if some see an intensifying threat in the latest verbal warning, others see a badly wounded Al Qaeda on the defense.
"If you look at this tape coming on the heels of the latest bombings in Saudi Arabia and Morocco, it tells me Al Qaeda has been really hurt," says Richard Schultz, director of the International Security Studies program at the Tufts University Fletcher School. "Saudi Arabia and Morocco were not in the high-value target area, like the embassy bombings, the bombing of the USS Cole, or 9/11."
Mr. Shultz says he thinks the message is, instead, a bold effort to make Al Qaeda adherents believe their group is still in the game.