Saddam touts urban war as his regime's ace in the hole, promising to bring the world power to its knees in a painful reminder of Somalia and Vietnam, two of the gravest failures in US military history.

But here on Kuwait's scorching desert plain, US Marines Corps infantrymen scoff at Saddam's threats and say they are ready to battle it out in the cities.

Baghdad is a maze of streets, mixing crumbling four-floor buildings from the Ottoman era, Stalinist-style government ministries and Soviet-era high-rise apartment complexes that could prove a snake pit for any invading army.

However, marines like Corporal Andrew Church, who attended a special school in urban combat, claimed there's nothing his troops cannot overcome in Baghdad.

"We train for the 360-degree threat," Church said outside his dusty green tent.

Fellow Corporal Nick Uruchurtu, 22, also a specialist in urban war, nodded in agreement.

The pair say a soldier must constantly angle his M-16 assault rifle or light machine gun to the side, rear or above as he prowls through the urban jungle, guarding his colleagues.

"Always have your head on a swivel. Where your muzzle goes, your eyes go," Church said.

In Baghdad, Saddam could unleash wave after wave of guerrilla forces like his Fedayeen militia of Baghdad toughs, his Special Republican Guard and other elements from his feared security apparatus.

But, while Saddam is publicly banking on sucking US troops into an urban death trap, the US military has quietly revamped its street-fighting tactics over the last seven to eight years.

Since 1997, the Marines have run an urban warfare research programe called Project Metropolis, which studied cases of street fighting, including the US army's dark hour in Mogadishu when 17 soldiers were killed and Russia's debacles in Chechnya since the mid-1990s.

"Looking at Grozny where casualty rates were outstanding at 80 percent, that was too high for the Marine Corps," said Captain Ron Storer, the training officer for the Marines Second Tank Battalion currently serving with the Regimental Combat Team Five, who worked on Metropolis until June.

In the Metropolis exercises, the marines rented out huge housing complexes and also constructed model cities to run intensive urban warfare drills, incorporating the gritty realities of third-world cities, which many top brass fear will be one of the main battlefields of the 21st century.

Storer described the wargames as dirty and no-holds barred.

"The enemy was a free-thinking enemy. There was nothing to restrict what he did. It was an asymmetrical threat, there only to inflict casualties -- to create the scenario you never want to see (on television) at home", he said.

Metropolis enabled the Marines to forge a crucible for urban battle where tanks and light armoured vehicles would patrol in tandem with ground troops.

Cities could be broken down on maps sector by sector, and all steps would be taken to guard infrastructure deemed valuable to the city's future.

Storer offered several scenarios:

Two Abrams battle tanks paired with a four-man team of riflemen barrel their way through an enemy line, the tanks punching ahead while the marines on their flank and rear covered sewer manholes, rooftops and alleyways.

A four-man squad comes under sniper fire and calls for back-up. Another crew of 12 or more marines block off the sniper's escape routes, throwing the gunman into a panic. A team of combat engineers blows out a wall and enters the building's ground level, or a Cobra helicopter swoops down on the roof.

"It's the OODA-LOOP," said the sunglassed, buzzcut Storer, tossing out the marine slang for confusing the enemy.

He drew attention to Saddam's possible Achilles heel: can his regime, tarred by its reputation for mass human rights violation, count on his people's loyalty when the Americans come to town?

"Get inside the mind of the enemy. Get his brain going 100 miles per hour, hitting him with ground and air. It's going to cause him to overload and break down," Storer said.

The captain had no doubt Saddam wanted no replay of his disastrous 1991 Gulf War defeat in the open desert terrain and would try to lure the US military into the cities.

"It could create problems with refugees and dealing with the local population, but not enough so we couldn't complete our mission," the captain said.