Coalition officials in Baghdad confirm that an American soldier was killed and three were wounded in an overnight attack north of the city.
U.S. military officials say the rocket-propelled grenade attack was directed at a convoy north of the capital, around the area of Balad.
The attack on the 4th Infantry Division brought to 53 the number of U.S. soldiers killed in hostile action in Iraq since President Bush declared major combat over in Iraq on May 1.
U.S. military officials say die hard Saddam Hussein loyalists and some foreign mercenaries are behind the guerilla attacks. But some Iraqis say they believe the assaults are being carried out by nationalists who want to force the U.S. coalition troops out of the country.
Soldiers of the 4th Infantry Division also carried out a sweep of Saddam's hometown of Tikrit overnight, and arrested a man suspected of organizing attacks.
U.S. officers say they have stepped up their efforts in hopes of closing in on Saddam himself.