WASHINGTON — The Army is fixing the doors of every armored Humvee in combat in Iraq because the doors can jam shut during an attack and trap soldiers inside, Pentagon records and interviews show.

The door trouble, the latest in a series of problems with the Humvees since the Iraq war began, is an unintended consequence of the Pentagon's effort to add armor to protect troops from makeshift bombs. So-called improvised explosive devices are the No. 1 killer of U.S. troops in Iraq, causing 70 percent of injuries and deaths. Armored Humvees, the primary troop-transport vehicle, are often targeted by insurgents who plant bombs on roads.

One quick fix to the jamming problem was to weld D-shaped hooks to Humvee doors so another truck could rip them off with a cable. The hook is built in to the latest version of armor added to the Humvee, known as the Frag Kit 5, said Lt. Col. William Wiggins, an Army spokesman at the Pentagon. "Every Humvee outside (a fortified base) will have a hook," Wiggins said. There are about 18,000 Humvees in Iraq.

The Army plans to spend $284 million this year on armor kits, which also include improved door latches and stronger hinges to handle the heavier doors. The money is included in the emergency Iraq spending bill President Bush vetoed earlier this month. Bush rejected the bill because it contained a timeline to withdraw troops from Iraq.

"The Humvee wasn't designed to withstand the kind of blasts our soldiers are getting hit with in Iraq," said Sen. Joseph Biden, D-Del. "This is just another reason why we need to get as many of the new MRAP (Mine Resistant Ambush Protected) vehicles as possible into the field, as soon as possible"

The MRAP vehicle has a V-shaped hull and a raised chassis that better disburses the force of a blast.

Biden recently won approval of a $1.5 billion amendment to the military spending bill to buy more MRAP vehicles. The Pentagon needs more than $8 billion this year and next to pay for about 7,700 vehicles.

The Pentagon does not generally identify vehicles in which troops are killed, making it impossible to determine how many troops were wounded or killed because of the door problem.

With the armor from the new kits, a Humvee door can weigh at least 600 pounds, said Rep. Gene Taylor, D-Miss., of the House Armed Services Committee.

The Humvee has run its course as a useful military vehicle, he said. "It wasn't designed for what it's doing now," he said. "It wasn't designed for urban warfare."

The Marine Corps intends to replace all their Humvees with the new vehicles. The Army plans to continue using the Humvees.

Signaling a possible change, Adm. William Fallon, in written testimony to the Senate Armed Services Committee this month, called "rapid fielding" of MRAPs a priority.

Fallon heads U.S. Central Command, which is responsible for the wars in Iraq and Afghanistan.

No Marine has died in more than 300 attacks on the new mine-resistant vehicles in Anbar province, according to Maj. Jeff Pool, a spokesman based in Fallujah.

The Marines have been welding eye bolts to their Humvees in Anbar province as well, Pool said.