Washington —- Hundreds of U.S. Marines have been killed or injured by roadside bombs in Iraq because Marine Corps bureaucrats refused an urgent request in 2005 from battlefield commanders for blast-resistant vehicles, an internal military study concludes.

The study, written by a civilian Marine Corps official, accuses the service of "gross mismanagement" that delayed deliveries of the mine-resistant, ambush-protected trucks for more than two years.

Cost was a driving factor in the decision to turn down the request for the so-called MRAPs, according to the study.

Stateside authorities saw the hulking vehicles, which can cost as much as a $1 million each, as a financial threat to programs aimed at developing lighter vehicles that were years from being fielded.

After Defense Secretary Robert Gates declared the MRAP the Pentagon's No. 1 acquisition priority in May 2007, the trucks began to be shipped to Iraq in large quantities.

The vehicles weigh as much as 40 tons and have been effective at protecting American forces from improvised explosive devices (IEDs), the weapon of choice for Iraqi insurgents. Only four U.S. troops have been killed by such bombs while riding in MRAPs; three of those deaths occurred in older versions of the vehicles.

"If the mass procurement and fielding of MRAPs had begun in 2005 in response to the known and acknowledged threats at that time, as the [Marine Corps] is doing today, hundreds of deaths and injuries could have been prevented," the study's author, Franz Gayl, writes.

"While the possibility of individual corruption remains undetermined, the existence of corrupted MRAP processes is likely, and worthy of [inspector general] investigation," said Gayl, the science and technology adviser to Lt. Gen. Richard Natonski, who heads the Marine Corps' plans, policies and operations department.

Gayl, who has clashed with his superiors in the past and filed for whistle-blower protection last year, used official Marine Corps documents, e-mails, briefing charts, memos, congressional testimony and news articles to make his case.

Maj. Manuel Delarosa, a Marine Corps spokesman, called Gayl's study "predecisional staff work" and said it would be inappropriate to comment on it.

Last year, the service defended the decision to not buy MRAPs after receiving the 2005 request. There were too few companies able to make the vehicles, and armored Humvees were adequate, officials said then.