OSHKOSH, Wis. — A new combat truck with a V-shaped bottom designed to withstand blasts from roadside bombs is performing with such success in Iraq that the U.S. military is pressing a Wisconsin company and others to churn out hundreds more in the coming months.

About 200 prototypes of the Mine-Resistant Ambush-Protected vehicles have been deployed in Iraq since 2004, said Capt. Jeff Landis, spokesman for the Marine Corps Systems Command in Quantico, Va. No Marine has died while in one of the trucks, Landis said.

"This is the best vehicle available for safety and survivability," he said. "The MRAP vehicle supplies troops with the greatest protection we've had."

Force Protections Industries in Ladson, S.C., built the 200 prototypes. Within the past month, the Pentagon awarded about $210 million in contracts to Force Protections, Oshkosh Truck Corp., and three other companies in the U.S. and Canada to manufacture a total of nearly 400 more vehicles. Landis said the military hopes to receive them by the end of the year.

The key is the truck's V-shaped steel body, which flares like the hull of a boat, said Oshkosh Truck spokesman Joaquin Salas.

"The shape channels the full force of a blast up the sides of the vehicle rather than through the floor," Salas said. "It's all physics. Vehicles with that shape are extremely effective."

Since the war began, more than 3,160 U.S. service members have died in Iraq. Roadside bombs account for 70 percent of U.S. deaths and injuries in Iraq, according to Defense Department records and testimony.

The Pentagon has been criticized for supplying insufficient armor for Humvees, the standard vehicles used for transport. The military has since fitted thousands of Humvees with additional armor. But most of the surfaces on a Humvee's underside are flat, creating a large area that catches the force of land-mine blasts.

The new vehicles also have tires that can be driven on even when flat.

Commanders in Iraq originally said the military would need 4,100 mine-resistant vehicles, but raised their request to 6,738 in February after seeing how well the trucks protected occupants, Landis said. Those requests are subject to approval by Congress.

The trucks come in three categories, from the small — a 7-ton truck that holds six passengers — to the 22 1/2-ton mammoth that carries 12 passengers. By comparison, General Motors' Hummer H3 weighs about 3 tons and a military tank around 71 tons.

Despite the new trucks' protective strength, military officials said they do not believe they will completely displace lighter, more maneuverable vehicles.