"A coalition forces soldier died of injuries sustained during an explosively formed projectile (EFP) attack on a convoy" south of the Shiite holy city of Karbala, the military said in a statement.
An EFP is a sophisticated type of roadside bomb that the US military has long accused neighbouring Iran of supplying to armed groups in Iraq.
The latest death brings the total number of US casualties since the March 2003 invasion to topple Saddam Hussein to 4,273, according to an AFP count based on the independent website icasualties.org.
On Friday five US soldiers were killed by a suicide truck bomb in the northern city of Mosul in the deadliest attack on troops in more than a year. A sixth soldier was killed in a roadside bomb Sunday north of Baghdad.
