The soldiers, from the 1st Armoured Division, were fired on while providing security at a weapons cache found in a raid the previous night, the statement on Monday said.
The latest fatality brings to 553 the number of US troops killed solely in combat since the invasion of Iraq in March last year.
Iraqi policeman killed
Earlier, an Iraqi policeman was killed and six others hurt after an attack on a US occupation base outside the city of Najaf.
Smoke was seen rising after resistance fighters traded fire with US troops at the base between Najaf and nearby Kufa, 130km south of Baghdad.
One Iraqi policeman was killed and six civilians were injured, two of them seriously, said Sadh Jader Hussain, from Najaf's Hakim General Hospital.
Spanish and Latin American
troops recently exited Najaf
Reports said that up to 30 mortar rounds were fired at the base where US occupation troops had recently replaced Spanish and Latin American troops.
"I heard the exchange of fire between the people at a checkpoint and the militiamen," said local resident Yaff Abd al-Khodir.
"I saw a burning vehicle in the neighbourhood and took two wounded people to the hospital."
A spokeswoman for the US-led occupation in Baghdad had no immediate details of the clashes.
Clashes on Sunday killed nine US soldiers across the country. In the heaviest attack, five Navy sailors and one Army soldier were killed in a mortar barrage against a base near Ramadi, west of Baghdad.
More killed in Mosul
In the northern city of Mosul, two Iraqis were killed when they came under fire from US troops, the US military said on Monday.
The military said the two were busy planting a roadside bomb. The device exploded during the shooting, killing the pair, said spokesman Colonel Joseph Piek.
US convoys have been regularly targeted by resistance fighters in and around the city, 370km north of Baghdad.
US military vehicles are regularly
attacked by resistance forces
In the western town of Baquba, also north of the capital, an unknown number of US soldiers have been injured in a rocket-propelled grenade attack targeting their patrol, eyewitnesses told Aljazeera's correspondent in Iraq.
A US military vehicle was also damaged in the attack, the correspondent added.
Meanwhile, IGC members Ahmad al-Chalabi and Muhammed Bahr al-Ulum, and Supreme Council for Islamic Revolution member Adil Abd al-Mahdi said they support the Iraqi Defence Minister's refusal to consider Republican Guards in Falluja a part of the new Iraqi army.
In a statement received by Aljazeera, the three said the decision was a US military initiative, holding the US Marines responsible for what they have called "threatening Iraq's security and future".
Tribal leader detained
Meanwhile, a leading Shia Muslim tribal leader in Iraq's northern Kirkuk region has been arrested by US occupation troops for allegedly supporting attacks on oil pipelines.
"American soldiers last night arrested Shaikh Kazim Ahmad, head of the Al-Badir clans, in the Hittine area," about 30km north of Kirkuk, said a member of the regional council, Karim Hassan.
He said the soldiers found a large quantity of weapons during the arrest, including rocket propelled grenade launchers and mortars.
Iraq's northern pipelines, notably the one leading to Turkey's Ceyhan terminal on the Mediterranean are regularly sabotaged, interrupting the country's vital crude exports.