The officials, briefing reporters at the Pentagon, said they have solid evidence that Iraqi President Saddam Hussein intends to create a humanitarian crisis that would stymie any US advance and turn international opinion against the war. The officials spoke on the condition of anonymity.

US intelligence officials also believe Saddam will use his biological and chemical weapons if he believes he is about to fall, even in the opening days of a war. His primary targets: US forces in Iraq, as well as the populace in his longtime enemies of Israel and Kuwait, the officials said.

Iraq can deliver these weapons with Scud and other missiles, aircraft-mounted sprayers and artillery shells, the officials said. They expect Iraq to use disease weapons like anthrax, poisons like botulism and ricin, and mustard gas. He is not believed to have any nuclear weapons.

He may also use them against his own populace, particularly against Shi'ite Muslims who have opposed him the past, the officials said.

Iraq maintains it destroyed all of its chemical and biological weapons. And for all their fears, the US officials acknowledged a lack of specific information about Saddam's weapons stockpiles.

US officials have pointed to lists of warheads that UN inspections have not accounted for, new activity at old weapons-manufacturing sites, and imports of suspicious equipment as evidence of Iraq's intentions to develop new weapons.

While the officials said Iraq's conventional military forces are in worse shape than they were during the 1991 Gulf War, they said there are a number of unknowns that could make any US offensive less than easy.

A rapid takedown of Saddam's regime may key on military and popular uprisings against him and his security forces in Baghdad, even as US forces close in, officials said. But knowing when and if his military chiefs would turn against him is difficult.

Whether the US military could stop chemical and biological weapon strikes is another unknown, officials acknowledged. They also fear - but have little evidence of - Saddam turning to al-Qaida or other Islamic extremist groups to conduct terrorist attacks.

Saddam has been preparing for a war with the United States and its British allies since the weeks after the Sept. 11 attacks, the officials said.

But instead of planning to engage US forces in the open desert along Iraq's borders, as in the Gulf War, his military has prepared a multi-layered defense, with Baghdad at the center. His forces are expected to use rivers and other terrain features as natural obstacles to the US advance, but Saddam isn't expected to put up much of a fight for large southern cities like Basra.

On the outermost ring is Saddam's regular army, probably less than 300,000 troops. The intelligence officials painted a picture of a war-weary mainstay Iraqi military force, short on spare parts, training and modern weapons, and predicted it would wall within days against a concerted US attack. His air force, mostly old jet fighters, is not regarded as a major threat.

Six divisions of his Republican Guard, with about 80,000 troops, constitute the next innermost layer. Many of these units operate closer to Baghdad. These units have the best equipment, plenty of tanks and better-trained soldiers, officials said.

These units have been receiving trucks given to Iraq under UN-sponsored oil-for-food programs. They have also been resupplied by spare parts smuggled through Syria. US officials believe the Syrian government has given tacit approval to this smuggling in defiance of UN sanctions against Iraq enacted after the Gulf War.

Inside Baghdad proper are internal security forces that are particularly loyal to Saddam, notably his Special Republican Guard, of about 10,000 lightly armed fighters, who, nevertheless, present a threat as urban fighters who are less likely to break ranks and flee or surrender.

Combat in Baghdad proper could also further Saddam's ends of creating a humanitarian crisis, as the civilian population is sure to suffer, either from errant US bombs or Saddam's reprisals against his own people.

It could also be difficult for American troops. Urban fighting is inherently deadly, as many US military technological advantages are mitigated by the close quarters of street-to-street fighting.

One improvement in Saddam's military has been in communications, officials said. Chinese and Turkish companies have helped Iraq lay a nationwide fiber-optic network that is difficult for US forces to cut off and to spy on.

This allows surface-to-air missile sites, for example, to relay sightings of US aircraft to each other, the officials said.

(China Daily December 19, 2002)