Two US soldiers have been killed and another injured in a Kurdish-controlled area of northern Iraq where attacks on American forces have been rare.
US soldiers are being killed almost daily in Iraq
The soldiers - from the 101st Airborne Division - came under attack near Tal Afar, just west of the northern city of Mosul.
Their convoy was attacked by rocket-propelled grenades and small arms fire, said military spokesman Corporal Todd Pruden.
All three soldiers were rushed to a military hospital, where two of them died, bringing to at least 34 the number of US soldiers killed in action since President W Bush declared major combat operations over on 1 May.
In a separate incident on Sunday, an Iraqi driver was killed and three other people were injured when a two-car UN convoy was fired on near the southern city of Hilla.
Most of the recent violence has occurred in an area north and west of Baghdad called the Sunni triangle, where some support for Saddam Hussein remains.
The US military says the attacks are carried out by hardliners loyal to the ousted President Saddam Hussein, who is believed to be in hiding in Iraq and issuing taped messages urging supporters to attack the Americans.
US Secretary of State Colin Powell acknowledged on Saturday that it would take some time to stem the "guerrilla-type" attacks, echoing assessments from US civil administrator Paul Bremer and Defence Secretary Donald Rumsfeld.
The deaths bring to 151 the number of American soldiers killed in action since the start of the war - four more than the total killed in the 1991 Gulf war.
Failure to elect leader
In another sign of growing Iraqi resentment towards the US-led occupation force, up to 10,000 demonstrators held an anti-American rally in the holy Shia city of Najaf, south of Baghdad.
The governing council has faced protests in Baghdad
The demonstrators tried to march to the US military headquarters in the city, but were stopped by lines of American troops. No violence has been reported.
The march followed Friday's sermon by a prominent Shia cleric, Moqtada al-Sadr, who criticised the new Iraqi Governing Council, set up by the US administration, and called for the creation of an Islamic army.
On Saturday protesters in Baghdad accused US forces of harassing Mr al-Sadr by surrounding his house.
The coalition troops have denied the charges.
The Najaf rally came a day after the Iraqi Governing Council had failed to choose a single leader, opting instead for a three-person rotating leadership group.
The BBC's Jonny Dymond, in Baghdad, says the council's failure to choose a single leader will be interpreted as a sign of weakness.