An audit of US-funded reconstruction projects for Iraq has found millions of dollars have been wasted because many schemes have never been completed.
The Special Inspector General for Iraq Reconstruction blamed delays, costs, poor performance and violence for failure to finish some 855 projects.
Many other projects had been falsely described as complete, found the audit of 47,321 reconstruction projects.
Iraq reconstruction has cost US taxpayers more than $100bn so far.
USAID, the body responsible for overseeing Iraqi reconstruction, has responded that the database used for the review was incomplete.
The audit by Senator Stuart Bowen found US officials had terminated at least 855 projects before completion.
Of this number, 112 were ended because of the contractors' poor performance.
Danielle Brian, executive director of the watchdog group Project on Government Oversight, said: "The report paints a depressing picture of money being poured into failed Iraq reconstruction projects.
"Contractors are killed, projects are blown up just before being completed, or the contractor just stops doing the work."
Last year, congressional investigators said as much as $10bn (£5bn) charged by US contractors for Iraq reconstruction had been questionable.