Resistance fighters fired three rocket-propelled grenades at a support convoy on a main road northeast of Ba’quba, 70km northeast of Baghdad, on Friday morning, said Captain Jay Miller from the 67th Armour Regiment's 3rd Battalion.
Small arms fire also hit the group. One of the wounded soldiers would have to have a leg amputated, said Captain David Nelson from the 4th Infantry Division's 2nd Brigade.
The soldiers belonged to the 8th Infantry Regiment's 2nd Battalion and were travelling from the town of Muqdadiyah to 2nd Brigade headquarters in Ba’quba, he said.
The soldier's death raises the number of American soldiers killed in Iraq to 282, of which 67 have died in combat since 1 May, when US President George Bush declared an end to major combat operations in Iraq.
Speaking to reporters on Thursday the commander of US forces in Iraq, Lieutenant General Ricardo Sanchez said casualty figures since the end of major conflict were "about what we would expect to get in this kind of conflict".
Meanwhile, a car exploded near the main British military base in the Iraqi city of Basra on Friday but there were no casualties, witnesses said.
The blast, which caused a fire that was quickly extinguished, damaged two cars around 200 metres from the entrance to the base in the southern city.
The owner of one of the cars said someone had driven up to his vehicle and thrown an explosive device into it.
Britain's Ministry of Defence confirmed a "small explosion" had taken place near its headquarters in Iraq's second city.