Marine Major TV Johnson told reporters on Sunday that the attack targeted a military base around 100km from Falluja, but would give no further details.
Another US soldier was killed in a small scale attack on an occupation forces' military base near the northern city of Kirkuk.
"One US soldier was killed and 10 were wounded during an improvised explosive device and small-arms attack on a coalition base near Kirkuk around 09:00 (05:00 GMT) 2 May," the military said in a statement.
Another two American soldiers were killed in an attack in northwest Baghdad at 04:45, while a third and two members of the paramilitary Iraqi Civil Defence Corps were also wounded.
In southern Iraq, two US soldiers were killed when resistance fighters fired on a convoy with small arms and rocket-propelled grenades in the city of Amara at about 19:00 on Saturday.
At least 745 US troops have died since the start of the US-led invasion of Iraq in March 2003, according to a tally based on Pentagon figures.
An end to resistance on 30 June
never seemed likely
More than 10,000 Iraqis are also estimated to have been killed.
More of the same
A senior US military officer in Iraq warned on Sunday there was no end in sight to resistance, predicting more violent attacks against occupation forces until 2005.
The officer said the public should not expect an end to attacks until there was an elected administration.
He also called into doubt the occupation administration's claim that the installation of an interim Iraqi government on 30 June would deflate the insurgency.
"The important thing to remember is it's only an interim government and it's not an elected government".