The highest ranking U.S. military intelligence official said yesterday that there is "a very real likelihood" that Iraq's military could quickly collapse, citing evidence that one of the most extensive "psychological operations" campaigns ever waged has triggered movements by civilians and military personnel.

"We're prepared for a situation where the Iraqi military offers stiff resistance and is organized in its execution of military operations," said Vice Adm. Lowell E. "Jake" Jacoby, director of the Defense Intelligence Agency (DIA). "There is a very real likelihood, though, that resistance could collapse very quickly."

In his first interview since taking the helm at the DIA last summer, Jacoby declined to specify what types of activities the agency is seeing on the ground in response to the military's "psyops" campaign of leaflet drops and radio broadcasting.

But he said he believes that "the messages are being received and are probably shaping people's future behaviors. I think the president last evening was very clear in terms of the way ahead."

In a televised address to the nation Monday night, President Bush gave Iraqi President Saddam Hussein and his two sons 48 hours to leave the country before the United States and its allies would begin military action to depose and disarm the Iraqi regime. Bush also urged Iraqi troops not to fight the U.S. military and said that the U.S. military would give "clear instructions" on how Iraqi units should act to avoid being attacked.

Radio broadcasts and more than 14 million leaflets dropped across southern Iraq, including 360,000 yesterday, have urged soldiers to abandon Hussein's "corrupt" regime. The leaflets and broadcasts have also warned them not to use weapons of mass destruction and not to destroy Iraq's oil infrastructure.

Whatever success the psyops campaign is having, intelligence reports indicated that Iraqi forces have begun opening the spigots on oil wells in the country's southern oil fields. "Flowing oil and soaked earth are a lot harder to extinguish than a well that just blew up," said one intelligence official, who asked not to be quoted by name.

One reason DIA analysts believe a quick military collapse is likely, Jacoby said, stems from experience with dictatorial regimes. "There's some point in time when people cease to fear the regime and the despot, and they act on a new set of circumstances, because you can't compel loyalty," he said. "You can compel compliance, but not loyalty."

Other defense and intelligence officials at the Pentagon reported, meanwhile, that Iraqi military units, including all six elite Republican Guard divisions, have dispersed outside their barracks. "They're trying to ride out the first attack," a defense official said.

Part of one Republican Guard division, the intelligence official added, has been spotted moving south toward Baghdad.

There is also some anecdotal evidence, from intercepted e-mails to cell phone calls, that the psyops campaign has unnerved regular troops and the Iraqi civilian elite, the intelligence official said.

Pentagon officials cited one report in the British media about a small group of Iraqi soldiers trying to surrender to British forces just over the Kuwaiti border and being sent back.

Still, the defense official cautioned that there is no hard evidence of mass surrenders being prepared. Regular Iraqi units are at their posts along the Green Line separating Iraq from the Kurdish-controlled north.

"It reminds me of the saying, 'I'll believe it when I see it,' " the official said.

Jacoby said Iraq has concentrated its air defenses around Baghdad, and may move its most disciplined troops to the capital as well. "We're still projecting that the most loyal units to [Hussein], the ones that have the most to lose because they are tied to the regime, will move back to the Baghdad area," he said.

Concentrating air defenses around Baghdad probably will not enable Iraq to shoot down a U.S. aircraft, given the antiquated nature of the antiaircraft batteries in and around Baghdad, the defense official said.

But it will force pilots to fly higher and sacrifice some degree of precision targeting. Those antiaircraft sites also could make the U.S. military wary of operating helicopters at low altitudes in the capital, which would make it more difficult to provide close air support to troops fighting in the city.

Jacoby said he remains firmly of the belief that Hussein will use chemical or biological weapons against invading U.S. forces. "This person has used [chemical weapons] on his own population, has used it previously, he's crossed that inhibition line," he said. "The question we're normally asked is, 'Well, when might he employ?' And our assessment is, when he believes the regime is going down."

Defense officials said one source in the region has told U.S. officials that artillery shells packed with chemical weapons -- most likely mustard gas or some kind of binary nerve agent -- have been shipped to a Republican Guard unit in the south, near the town of Al Kut.

But defense officials expressed skepticism about that report, saying they had no hard evidence. At the end of the Persian Gulf War, Iraqi prisoners gave detailed information about the artillery rounds armed with chemical weapons and how they had been distributed. Despite those efforts, commanders did not fire any chemically armed shells.

There is also worry that Iraq's aging fleet of MiGs, no match for U.S. pilots, are being outfitted with sprayers and will be used on suicide missions once U.S. forces have penetrated deep into the country.