In the last six days, US troops have shot at Iraqi police, journalists, a wedding party and a top Italian diplomat searching for looted antiquities.
The Americans are under increasing pressure as the guerrilla resistance has stepped up its hit-and-run attacks and is bringing more firepower and sophistication to the fight.
Unsure of who will shoot at them next, the US forces have been involved in "friendly fire" attacks in which 10 civilians have been killed in the past two months.
"We are facing an adaptive, asymmetric enemy, and we, of course, are adapting and refining our tactics, techniques and procedures as well," Lieutenant-Colonel George Krivo, a US military spokesman, said on Friday.
In areas where resistance is stiffest, the massive response by US soldiers is changing once-neutral residents into outright opponents.
"The killing of the policemen was the turning point for me," said Sabah Khalaf, recalling the Sept. 12 friendly-fire killing of eight US-allied Iraqi policemen in Fallujah, one of the most dangerous cities for American forces.
Soldiers from the US Army's 82nd Airborne Division killed the policemen as they chased a highway bandit. The US military apologized for that incident and opened a high-level investigation.
"I thought they came as liberators and had hope that they would bring this country freedom," said Khalaf, a 31-year-old resident of Fallujah. "Initially, we were against the police, calling them agents of the Americans. But by killing the police, the Americans showed their true faces.... I think the attacks against them will increase, and revenge for the dead policemen will be taken."
In the most recent friendly-fire incident, American soldiers in northern Iraq shot at a car carrying the Italian official heading up US efforts to recover Iraq's looted antiquities. Pietro Cordone, the top Italian diplomat in Iraq, was only superficially wounded and his wife was unhurt, but his Iraqi translator was killed.
Cordone, also the senior adviser for cultural affairs of the US provisional authority, was traveling on the road between Mosul and Tikrit on Thursday when his car was fired on at a US roadblock, according to an Italian Foreign Ministry official, who spoke on condition of anonymity.
Cordone, interviewed on Italian state television, said an American soldier motioned for the car to switch lanes, then fired one shot after the driver failed to move the car quickly enough.
"The shot went through the interpreter's heart, went out his back and grazed me on my arm," the diplomat told reporters, looking dazed a few hours after the shooting. "We didn't violate any checkpoint," he said.
The Italian Foreign Ministry said US officials had expressed regret over the incident. In Baghdad, the US military said it was investigating.
Also Thursday, US soldiers shot up the car of an Associated Press photographer in Khaldiyah during a firefight after an American convoy was hit with a remote-controlled roadside bomb. The photographer, Karim Kadim, and his driver jumped from the car and ran for cover after they saw that a tank had them in its sights. They were fired on as they ran and the car was badly damaged in subsequent shooting. Neither man was hurt.
In the same incident, AP correspondent Tarek al-Issawi was shot at by soldiers using their tank's 50-caliber machine gun. Al-Issawi also escaped injury.