U.S. military officials have sent 14-thousand more soldiers to Iraq since last month to provide security during next week's constitutional referendum.
The Pentagon reported that 152-thousand troops are in Iraq on Thursday.
In Baghdad Thursday, a suicide bomber blew himself up on a bus, killing at least 10 people, and an American soldier died in a separate blast.
Officials in the northern city of Kirkuk said gunmen killed five oil facility security guards.
Meanwhile, Iraq's President Jalal Talabani met Britain's Prime Minister Tony Blair in London and said the presence of U.S. and British troops was vital to Iraq.
After their meeting, Mr. Blair warned that Iran or Lebanese Hezbollah militants may be providing bomb technology to Iraqi insurgents.
Tehran and Hezbollah denied the charges