A civil war in Iraq would be the US military’s sternest test since the 2003 invasion and some analysts say the troops could even be forced to withdraw.

Sectarian killings since the February 22 bombing of a Shi’ite shrine have taken hundreds of lives, threatening a conflict even deadlier than the Sunni-led insurgency of the past three years.

Nearly 2,300 American troops have already died in Iraq, but casualty risks would multiply if US forces were drawn into a conflict where they became targets for combatants on all sides.

Even US military chiefs do not rule out civil war. The US commander in Iraq, General George Casey, thinks the crisis sparked by last month’s Shi’ite shrine bombing is past, but asked if civil war could erupt, said: “Anything can happen.”

Defence analysts consider such a conflict could be near.

“If full-scale civil war erupts — and Iraq appears to be awfully close to that at this point — even 134,000 troops could be in a highly vulnerable position, especially when you consider how many true combat troops we have there,” said Ted Carpenter, defence analyst with the Cato Institute in Washington.

Many US troops in Iraq are supply and logistics personnel. British and Australian combat troops are not expected to make much difference should a bloody free-for-all erupt.

The military could try to stiffen the resolve of Iraqi forces to maintain government authority, by shipping in another US division of about 20,000 troops or by inserting special forces.

But that scenario assumes US-trained Iraqi troops and police would remain loyal in a crisis to the national government, rather than to religious leaders or the sectarian or ethnic militias to which many of them once belonged.

In the worst case, US troops could be forced to withdraw, leaving Shi’ite and Sunni Arab Iraqis at each others’ throats and other conflicts possibly ripping the country apart.

“You could be confronting situations where there would be full-scale firefights between rival factions,” Carpenter said. “If those divisions explode into massive violence, the US is in a hopeless situation.”

After a minibus bombing killed five people last week in Baghdad’s Shi’ite slum district of Sadr City, an official in the movement of firebrand Shi’ite cleric Moqtada al-Sadr said his Mehdi Army militia would take on security duties. The US military, which mauled the Mehdi Army in two uprisings led by Sadr in 2004, has vowed to block this.

“We are not going to allow him to take control of security of any area across Iraq, nor would the Iraqi government,” said Major General Rick Lynch, a spokesman for the US military.

Sunni Arabs, who suspect the Mehdi Army is behind many of the recent reprisal killings, have long accused the Shi’ite-controlled Interior Ministry of running death squads to avenge insurgent attacks on Shi’ites, a charge it denies.

Kurds, who fought alongside US forces during the invasion, are disproportionately represented in the new Iraqi army.

“Iraq’s Sunnis perceive the ‘national’ army and police force as a Shi’ite-Kurdish militia on steroids,” wrote US analyst Stephen Biddle in a recent report that questioned the US policy of turning over security responsibility to Iraqi forces.

“Removing the United States from the scene means eliminating the player most loyal to the idea of a stable, heterogeneous Iraq,” wrote Biddle, Senior Fellow in Defence Policy at the Council on Foreign Relations. — Reuters