The U.S. Defense Department says the increased pace of American military operations in Iraq is responsible for the high U.S. death toll this month.
A Pentagon spokesman, Brigadier General Perry Wiggins says the presence of more U.S. troops in Baghdad is creating progress but also casualties.
He described May as a "tough month."
The Pentagon says 115 U.S. troops have been killed in Iraq so far in May, making it one of the deadliest months of the war for U.S. forces.
The U.S. military says all 20-thousand additional combat troops President Bush ordered to Iraq have now arrived.
In other news, U.S.-led coalition forces in Iraq handed over security responsibilities Wednesday for three northern provinces of Dohuk, Irbil and Sulaymaniyah to the autonomous Kurdistan government. Seven of Iraq's 18 provinces are now responsible for their own security.
Also Wednesday, President Bush held a video conference with Iraqi leaders including Prime Minister Nouri al-Maliki and urged them to make progress on securing national unity and passing laws on sharing oil revenues.
In violence Wednesday, mortar attacks killed five people in Fallujah. Officials believe the mortars were fired at a U.S. military base but landed in residential areas.