The Pentagon said Tuesday it was more confident than ever in the MRAP armored vehicle, even after a soldier's death in Iraq showed for the first time that they are vulnerable to roadside bombs.

The soldier, a gunner who was partially exposed, was killed Saturday when a buried roadside bomb exploded with such force that it blew the Mine Resistant Ambush Protected (MRAP) vehicle into the air and caused it to roll over.

The explosion failed to penetrate the vehicle's crew compartment, however, and three soldiers inside escaped with broken bones in their feet and bruises, Pentagon press secretary Geoff Morrell said.

Morrell said that Defense Secretary Robert Gates, who the day before the attack had paid a high profile visit to a military factory that equips the vehicles, "is not questioning the protection provided by MRAPs."

"He is in fact more convinced than ever that these vehicles do indeed save lives," Morrell said.

Gates has championed the deployment of the MRAP vehicles, launching a crash program in May that has produced 2,225 of them.

Of those, 1,508 are already being used by US soldiers in Iraq and while 45 of them are in operation in Afghanistan, Pentagon officials said.

With a budget of 22.4 billion dollars, the MRAPs have emerged as the Pentagon's top acquisition program with 12,000 MRAPs on order and plans to increase the total buy to 15,400.

The vehicles have a V-shaped hull that are designed to deflect the blast of under-belly explosions, but are heavier than the armored HUMVEES they are replacing.

Gates was sold on them when he learned that no one had been killed in an MRAP in Iraq.

But the attack Saturday in Arab Jabbour on the southern outskirts of Baghdad show that even the more heavily armored MRAPS are not impervious to roadside bombs.

"We're still in our preliminary stages of reviewing this particular attack," Morrell said, adding that it was "a very large, deep-buried IED (improvised explosive device)."

"This MRAP — and, again, I don't know which model it was precisely — ran over that bomb. And the force of the explosion caused the MRAP to literally lift into the air and overturn," he said.

"Regrettably, of course, we lost the gunner," Morrell said, adding that it was still unclear whether he was killed by the blast or the rollover.

"But I think everybody is still amazed at the fact that, despite the size of this bomb, these vehicles are proving to be every bit as strong and as lifesaving as we hoped they would be," he said.