The Pentagon said Staff Sergeant George Alexander died on 22 October of injuries sustained earlier this month when a roadside bomb blew up near his vehicle in Samarra.
Shortly before the announcement, President George W. Bush said more sacrifices will be necessary before U.S. troops can come home.
It's not clear how many Iraqi civilians have died since the U.S.-led invasion, though one group that monitors press reports puts the death toll at more than 26,000.
Later today antiwar activists in the United States plan to gather at hundreds of events across the country.
Meanwhile, Al-Qaeda in Iraq said it has abducted two employees of Morocco's Baghdad embassy. No demands were made in the Internet statement, which could not be immediately verified.
(Compiled from agency reports)