Thirteen US troops were killed in violence across Iraq over the weekend, the US military has said.
US troops have suffered some of their worst losses in Anbar province
Four troops were killed when the helicopter they were travelling in crashed in Anbar province. About 150 Iraqis also died in the past two days.
Almost 2,900 US troops have now died in Iraq since the 2003 invasion.
The news came as US President George W Bush prepared to meet influential Iraqi Shia leader Abdel Aziz al-Hakim at the White House.
Four US troops died on Sunday when a marine helicopter carrying 16 people made an emergency landing on a lake near Haditha in Anbar province, the US military said.
"The incident does not appear to be a result of enemy action and is currently under investigation," the military said.
The US military said one soldier died in Baghdad and two north of the capital on Sunday.
On Saturday, one was killed north of Baghdad and five in Anbar.
On Sunday, the military also declared killed in action the pilot of an F-16 fighter that crashed in Anbar last Monday.