The US military said that one more soldier was wounded in the blast, which hit a patrol that was on a mission to clear a route of threats such as roadside bombs, the biggest killer of US troops in Iraq.
"Recently the unit has successfully found roadside bombs in the area, securing them so that explosive ordnance teams can arrive and recover the improvised explosive devices," the US statement said.
At least 2,975 US soldiers have been killed in Iraq since the US-led invasion in March 2003.
In another development, armed men kidnapped a senior trade ministry official in Baghdad after stopping his vehicle on his way to work.
A ministry source said that Muhanad Ahmed Saleh, director of the Baghdad international fair, was abducted in two vehicles shortly after he left his home in western Baghdad. No shots were fired.
Elsewhere, three Iraqi children were killed and eight wounded when they were hit by a roadside bomb on their way to school. The incident took place in the troubled northern oil hub of Kirkuk.
A police officer said the bomb exploded in the largely Turkmen district of Musala in northern Kirkuk shortly before 10am local time (0700 GMT) on Tuesday.
Captain Imad Jassim said two boys and a girl were killed and eight children wounded by shrapnel from the explosion as they were walking to the Amouriyah primary school.
All the casualties were children were under the age of 12, Jassin said. The dead girl and one of the boys who was killed were Kurds, and the other boy a Turkman.
Among the wounded were six boys and two girls.
In other news, a spokesman for Jalal Talabani, the Iraqi president, confirmed that US troops had detained two Iranians who were in Iraq at his invitation.
"The president is unhappy about it," said Hiwa Osman, Talabani's media adviser. He gave no further details, and the US military said it had no comment.