The incident took place on Sunday evening as a group of soldiers were moving through the district of Abu Ghraib on the western outskirts of the capital.
"A Task Force 1st Armored Division soldier and an Iraqi interpreter were killed and three other soldiers were wounded during an (improvised explosive device) attack on 21 March," a statement from the US military said on Monday.
The deaths raise to 396 the number of US soldiers and marines killed in combat since American forces invaded Iraq to overthrow Saddam Hussein a year ago.
Improvised explosive devices, in which explosive charges are hidden in soft drink cans, animal carcasses or other disguises and wired to a simple detonator, have become the most common and deadly technique used by fighters to attack US forces.
Finnish businessmen killed
Also on Monday, two Finnish business people on a trip to Iraq were shot dead by sniper fire in Baghdad, the foreign ministry said.
National Finnish broadcaster YLE said the two were killed at
09:00 GMT while on their way to the Ministry of Electricity.
It said the men were part of a delegation from the Technology Industries of Finland, which left the Nordic country on Saturday to lobby for Finnish business contracts in Iraq.
Finnish news agency STT reported the men were from unlisted engineering firms Ensto and Air-Ix. An official at Ensto confirmed their employee's death, but did not give any more details.
Officials at Air-Ix and the Technology Industries of Finland were not immediately available for comment.