It was not immediately known how many soldiers were wounded, Lt. Col. Dave Doherty, a military spokesman, said in a statement. He said a second interpreter was also wounded.
Doherty said the attack occurred in Ninevah province. He gave no more details, saying an investigation was ongoing.
An Iraqi police official said the attack took place in Mosul, a city in Ninevah province 225 miles northwest of Baghdad. Mosul is considered one of the last strongholds of Sunni insurgents.
The attack occurred about 3:30 p.m. when two people, who appeared to be Iraqi police officers, opened fire at a police checkpoint, said the official, who works at the Ninevah military command post.
Iraqi Brig. Gen. Saeed Ahmed al-Jubouri said the shooting wounded three U.S. soldiers and an Iraqi police captain. He said the gunmen fled in a car, and that police were searching for the attackers.
Al-Jubouri said the American soldiers were visiting with the Iraqi captain at the checkpoint at the time of the attack. He also said the interpreter was killed.
Tuesday's attack came a day afterduring fighting in Diyala province, an area northeast of Baghdad that continues to be volatile despite an overall drop in violence nationwide.
Two weeks earlier, a suicide car bomber struck a U.S. patrol in Mosul, killing four American soldiers and an Iraqi interpreter in the deadliest single attack against U.S. forces in nine months.
At least 4,250 members of the U.S. military have died in the Iraq war since it began in March 2003, according to an Associated Press count.