Baghdad, Iraq ? U.S. soldiers trying to calm Baghdad say the sprawling Sadr City slum has once again become a haven for anti-American militants – and the source of most of the gunfire and mortars directed at them.

In the past two weeks, U.S. forces have suffered several casualties from dozens of shootings, mortar attacks and roadside bombings that American troops believe originated from Sadr City.

Yet the Americans have been restrained in their response, as U.S. and Iraqi leaders strive to avoid a third confrontation in two years with firebrand cleric Muqtada al-Sadr and his Mahdi Army – the biggest and most dangerous Shiite militia in Iraq.

Instead of venturing into Sadr City in strength, U.S. troops are concentrating instead on the mostly Shiite neighborhoods that surround the militia stronghold. All the while they are drawing fire from Sadr City.

As a result, some American soldiers believe the only way – in the end – to curb Shiite militias and halt the sectarian violence will be to confront the militia fighters in their sanctuary.

Al-Sadr and his followers managed to rebound from defeats suffered at the hands of the U.S. military during two previous uprisings in 2004 – and have now emerged as a major political force.

Al-Sadr’s followers hold 30 of the 275 seats in the national parliament and five posts in Prime Minister Nouri al-Maliki’s Cabinet and are a major pillar of the prime minister’s support.

In August, al-Maliki, a Shiite, publicly berated the Americans for a raid on Sadr City.

With Americans facing political pressure to lay off al-Sadr, it appears unlikely the U.S. command will order a major operation against his base, home to an estimated 2.5 million people, without al-Maliki’s approval.

“We notify the prime minister if we’ve got sensitive targets and we let the prime minister know,” Maj. Gen. James D. Thurman, the commander of U.S. forces in Baghdad, told The Associated Press in a recent interview.

“We let him have a say, and we notify people. But if somebody is committing an act of violence, we’re going to go deal with it,” Thurman said.

In name, Sadr City is under the control of Iraqi forces, not the militia. When U.S. troops formally handed over the area to Iraqi soldiers in March, one Iraqi colonel promised, “We can handle the security inside Sadr City.”

But in reality, al-Sadr and his Mahdi militiamen call the shots in Sadr City. Few U.S. troops saw Iraqi troops, most of whom are also Shiites, on the major avenues where they were repeatedly attacked.

All that is frustrating to American soldiers, who believe the militias have a virtual sanctuary in Sadr City.

The Mahdi Army “claims they control Sadr City, and all the attacks are coming from Sadr City. Then (either) the (Mahdi Army) is doing the attacking or allowing others to,” said Capt. Chris L’Heureux, 30, of Woonsocket, R.I., a troop commander in the 4th Squadron, 14th Cavalry Regiment.

“It’s tough for a brigade like us that’s been (winning) … and here it’s all touchy-feely and paws off,” said 1st Lt. Bernard Gardner, 25, of Kinnear, Wyo.