A Task Force Baghdad Soldier died from a gunshot wound when his patrol in northeast Baghdad came under small-arms attack at around 3.30pm (1230 GMT) on Friday.
The soldier’s name is being held pending notification of next of kin, the US military said.
Earlier a car bomb blast killed two Iraqi civilians and wounded 15 others, including six US soldiers, in the northern Iraqi city of Mosul.
The US military said the soldiers wounded in the explosion on Thursday were all in a stable condition. There was, however, no word on the condition of the Iraqis.
US forces targeted
"The car bomb was driven by a suicide bomber. Two Iraqi citizens were killed. Six US soldiers and nine Iraqi civilians were injured," Sergeant John Franzen said.
Car bomb attacks occur nearly
daily throughout Iraq
Mosul, home to 1.5 million people, has been witness to frequent clashes between US-led forces and their armed opponents since November.
Aljazeera learned that two drivers carrying car bombs targeted a US military convoy in the Iraqi city of Haditha west of Baghdad.
Reports said the attacks left casualties among US soldiers but the US army did not comment further.