WASHINGTON —  For the second time since the Iraq war began, the Pentagon (search) is replacing body armor for U.S. troops in Afghanistan and Iraq, citing a need for better protection that can withstand the strongest of attacks from insurgents, a spokesman said Saturday.

The effort, which began more than a year ago, would upgrade the protection used by more than 500,000 soldiers as well as civilian employees and news reporters. The first upgrade installed ceramic protective plates in the vests and was completed in early 2004.

Defense officials acknowledge the replacement processes have been slowed in part by debates over what is best for the troops. The current replacement is expected to take several more months to complete, said an Army official, who requested anonymity because of the sensitivity of information affecting troop safety.

Pentagon spokesman Paul Boyce said Saturday, "Obviously, the body armor is manufactured and tested to exceptionally high standards. This is not the type of technology that is readily available from a local hardware store. It's very exact.

"But as new technologies emerge, the Army (search) works aggressively with the commercial industry to develop, test and produce the best possible equipment for our soldiers. Members of Congress have been briefed, and they have been fully supportive," he said of the latest replacement effort.

Maj. Gen. William D. Catto, head of the Marine Corps Systems Command (search), said he wasn't happy about the yearlong delay to replace the armor, noting that if defense officials had the capability, they would upgrade the protective garb right away. But he blamed the delay partly on a shortage of the raw material that is needed to strengthen the plates.

The new armor weighs about 18 pounds, about one pound heavier than the original plates, and consists of thicker plates that could shield soldiers against stronger attacks, according to the Army official.

The heavier weight was one factor that hindered a quicker change, the official said, pointing to concerns that soldiers might not be able to move swiftly in the face of an attack. The official declined to release additional information or specifics about how much armor had already been shipped to Iraq.

The New York Times first reported the Pentagon's efforts Saturday on its Web site. It said upgrades will cost at least $160 million. The Times said it withheld details of which insurgent munitions are able to pierce the older body armor to protect troops still using it in the field.