The soldier was evacuated from Samarra, 100km north of Baghdad, to a field hospital where he later died, a military spokesperson told AFP.
“A 4th Infantry Division soldier died of wounds he received in an RPG attack on his convoy which was travelling by Samarra,” at 17:00 GMT on Wednesday night, the spokesperson said.
The soldier’s death takes to 88 the number of Americans killed in combat in Iraq since US President George Bush declared an end to major hostilities on 1 May.
In a separate incident, a US soldier was shot to death and another wounded in an attack in Baghdad late on Wednesday, the US military said.
A bomb blast, earlier in the day, killed one US soldier and left two wounded in Tikrit, the hometown of Saddam Hussein. Tikrit lies about 175km north of the Iraqi capital.
Further north, Kirkuk remained restive. Two bombs were thrown at a job centre located near houses used by US troops in the centre of the city. There were no casualties.
“A black Mercedes car without license plates drove past the employment office. Two bombs were thrown towards the building but there were no casualties because the streets were empty at that time,” a local commander told AFP.