WASHINGTON - Iraq's military is significantly smaller and more poorly equipped today than it was a decade ago when it was routed in the Persian Gulf war but it retains the ability to inflict casualties on American-led forces should President Bush decide to forcibly remove Saddam Hussein from power.

Still the largest military force in the gulf region, Iraq could blunt or at least slow a threatened attack with chemical and biological weapons, an urban warfare strategy and the fierce resistance of Republican Guard units and internal security forces who have the best training and equipment, American and British military analysts say.

The Iraqi army, made up mostly of conscripts and down to 430,000 men from a high of nearly 1 million at the time of the gulf war in 1991, is said by defectors to suffer from morale problems in all but its most elite units.

In addition, Iraq's 2,200 tanks date mostly to the Soviet era, the majority from the 1950s, and nearly all are in dire need of spare parts. The air force has about 300 aircraft that may be operational, but just a handful of the sophisticated Russian-built MiG-29 interceptors that could challenge U.S. attack planes.

Iraq has no navy other than about 90 armed patrol craft.

Charles Heyman, editor of the defense journal Jane's World Armies, said the Iraqi fighting force has so deteriorated that "we are talking about a military that has by and large imploded." And William M. Arkin, a former Army intelligence officer and a defense analyst, dismissed Hussein's armed forces: "They were a paper tiger in 1991, and they're a tissue paper tiger today."

Former Iraqi Army Brig. Gen. Najib al Salhi, an armor officer who defected in 1995, recalled that the allied attacks of the gulf war, coupled with the U.N. sanctions, left his force in near-total disrepair. "I couldn't trust a tank to go 20 miles," he recalled. The morale of his troops, he said, "was very bad," a view expressed by other, more recent defectors, according to Iraqi opposition officials.

While the Iraqi forces have steadily declined, the U.S. military has spent the past decade modernizing, charging ahead in everything from precision bombs and unmanned spy drones to digital communications that can speed targeting information to a combat pilot or a tank commander.

But the Iraqis, for their part, have built up a fairly sophisticated and widespread air defense system since the gulf war. While the United States has chipped away at the system with repeated bombings during the past decade, the Iraqis continue to rebuild and improve the system with some of the billions of dollars collected from illegal oil sales and shadowy international deals.

Hussein, despite U.N. sanctions and bans on what he can purchase, has a network of suppliers. The Chinese in the past several years provided fiber optic cables that speed communications and, unlike microwave dishes, are buried, making them hard to locate and destroy. The Yugoslav military, which fought the United States in an air war over Kosovo in 1999, shared technical expertise with the Iraqis on evading and deceiving American pilots, defense officials said.

The North Koreans are suspected of shipping missiles or their components to Iraq. Ukraine is suspected of selling sophisticated radar and missile systems that could endanger U.S. attack aircraft, a possibility the Bush administration is investigating, Defense Secretary Donald H. Rumsfeld told reporters in a recent news briefing.

The Iraqis are also becoming adept at shifting around their mobile air defense systems and shooting at American and British aircraft patrolling Iraq's no-fly zones, set up after the gulf war to protect the Kurds in the north and Shiite Muslims in the south. "It's very, very hard to find things that are mobile," Rumsfeld said.

While none of these hazards would be a "show stopper," in the words of one retired Army officer, they amount to the troubling unknowns of warfare that could delay an allied military advance and drive up the number of combat deaths.

The low state of the Iraqi military "is a piece of the puzzle, but it's not the whole puzzle," said John Hillen, a defense analyst who served as an Army infantry officer during the gulf war. "The other piece is, Will they fight? I'm not sure if anyone has a good handle on that."

Large elite force

About 20 percent of the Iraqi Army, some 80,0000 men, makes up the Republican Guard or the Special Republican Guard, Hussein's personal security force. Many of the soldiers have kinship ties to the regime and receive the best equipment, such as the comparatively modern Russian T-72 tank. These soldiers protect the approaches to Baghdad and Hussein himself.

In addition, there are three paramilitary units that along with security and border guards total 24,000 men. Then there are Hussein's Fedayeen or "Men of Sacrifice," some 18,000 to 20,000 young soldiers who patrol Baghdad and have executed those disloyal to the regime.

Though many Iraqi soldiers surrendered or fled from allied forces during the gulf war, the Republican Guard fielded some of the few units who "fought ferociously," wrote Kenneth M. Pollack, a former CIA military analyst and author of the recent book, The Threatening Storm: the Case for Invading Iraq.

The Republican Guard, and especially the Special Republican Guard, includes more of Hussein's fellow Sunni Muslim tribesmen than in 1991, Pollack wrote. "If anything, this suggests they may be more willing to die for this regime."

A retired senior U.S. Army general, who fought in the gulf war and requested anonymity, agreed, saying, "You could get yourself caught up in a little bit of a gunfight with these guys. They could hurt us a little bit. I don't buy the argument they've been obliterated by 10 years of sanctions."

'Our worst nightmare'

Retired Army Gen. George Joulwan, former commander of U.S. and NATO forces in Europe, said it would be wrong to underestimate Hussein's elite troops. "They'll have a few units that will be particularly loyal, particularly if we get into the urban areas," he said.

It is that prospect, fighting block-to-block, especially among the 5 million residents Baghdad, that troubles some U.S. officers and military analysts.

Heyman, the editor of Jane's World Armies, said Hussein's forces would be destroyed by U.S. air power if they marched into the open desert. "What they can do is sit in the cities," he said, adding that the Iraqi dictator could position troops and tanks near schools and nurseries. "We can end up with a nasty standoff."

"That's our worst nightmare," said retired Rear Adm. Stephen H. Baker of the Center for Defense Information, an independent military research organization.

But others argue that U.S. forces, particularly the Marine Corps, have trained hard during the past decade in urban warfare. Moreover, they say U.S. spy drones and other sophisticated equipment could pinpoint enemy troop locations in the cities.

"It could be difficult, but it's not impossible," said retired Army Gen. Wesley Clark, former commander of NATO and U.S. forces in Europe, who led the allied attacks against Kosovo in 1999. Baghdad is not an ancient city of narrow, winding streets but a modern metropolis of wide boulevards, where U.S. forces could operate more easily, conquering the city by sections as they search for Hussein and his top aides, he said.

And al Salhi, the former Iraqi officer who defected, noted that the Special Republican Guard, while well-trained and equipped, is adept at putting down civilian uprisings, not facing a powerful army. "One thing they are lacking in," he said, "is experience in war."

But should a U.S.-led coalition reach Baghdad, there is the possibility that Hussein could launch missiles or shells filled with blistering mustard gas or the lethal nerve agent sarin. Or he might choose a deadly biological weapon such as anthrax. In the mid-1990s Iraqi officials admitted to producing 8,500 liters of anthrax and arming 25 Scud missiles with anthrax and toxins during the gulf war, although they did not use them.

Chemical warfare

This time, with Hussein himself the target, rather than Iraqi troops in Kuwait, the Pentagon predicts there will no longer be a reluctance to use weapons of mass destruction. Officials said Hussein has used the four-year absence of U.N. weapons inspectors to forge ahead with his chemical and biological programs.

"We expect him to use everything he has," said one senior Army officer, who said that Hussein could also target rear areas with such weapons, including ports and airfields used by U.S. troops.

The Iraqi dictator could also attack Israel with these weapons, a move that might win support among Arabs in the region who are increasingly bitter toward the United States and the spiraling Israeli-Palestinian violence.

"I think the principal thing they're worried about is a rocket attack on Israel," said a former CIA official with close ties to the Pentagon. In 1991, some 39 Scuds were fired at Israel from Iraq, although there were no deaths. A first order of business would be to use airstrikes or Special Forces soldiers to try to locate and destroy Scud sites in the western part of Iraq, he said.

What is uncertain, however, is the reliability of Hussein's Scud missiles - now numbering anywhere from 10 to 20 - artillery pieces and unmanned drones that would be used as delivery systems for chemical and biological weapons. During the gulf war, neither allied air power nor Special Forces soldiers damaged a single Scud, said Anthony H. Cordesman, an analyst with the Center for Strategic and International Studies.

But Pollack and other analysts observe that Iraq has never fired a Scud missile with a chemical or biological warhead, which they say is technically difficult. And if Hussein's forces were able to fire germ- or chemical-laden artillery rounds, they would immediately be spotted by U.S. radar. "Most Iraqi artillery batteries would be lucky to get off more than a few rounds before they were silenced by American guns," Pollack wrote in The Threatening Storm.

The Iraqi armed forces have a sophisticated air defense system and some elite troops who might or might not put up a fight, he said. But because Hussein has yet to develop a nuclear weapon, there is nothing that can compel the United States to avoid invading his country.

"He has no decisive military capability," Hillen said.