In April, 104 soldiers were killed, the Web site icasualties.com -- maintained by the Iraq Coalition Casualty Count -- said. The U.S. Department of Defense has confirmed 3,439 U.S. military deaths in Iraq, and 13 more await confirmation.

At least five U.S. military personnel were killed Saturday, three in a car bomb in Salahuddin Province and one south of Baghdad, The Los Angeles Times reported. A Marine was killed in Anbar Province.

U.S. casualties dropped early in 2007. President George W. Bush developed and announced his "surge" strategy after 112 soldiers were killed in December, making it one of the deadliest months of the war.

The administration and military leaders have warned that increasing the number of troops in Iraq and giving them a more active role in counterinsurgency work in Baghdad was likely to increase the number of casualties.