U.S. Defense Department statistics show through June 2008, there were 93 attacks on 6,100 logistics and supply convoys in Iraq, an average of about 1.5 percent. That compares to an attack rate as high as 20 percent in late 2006 and early 2007, USA Today reported Tuesday.

The convoys are carried out by Iraqi companies and use local drivers to deliver building materials for U.S.-sponsored reconstruction projects as well as equipment for Iraqi security forces, the newspaper said. It noted there are also more convoys on the road this year.

"The improved security obviously is allowing us to move more (supplies), but there also has been a large increase in demand for the services," Col. Gary Pease, an Iraq regional chief of staff for the U.S. Army Corps of Engineers, told USA Today.