Meanwhile, testing is under way on "MRAP II class vehicles," which will be heavier and costlier than vehicles in use now, said John Young, undersecretary of Defense for acquisition, technology and logistics.

MRAP vehicles have V-shaped hulls to deflect blasts from underneath and provide greater protection from roadside bombs than up-armored Humvees.

Each service's request for MRAP vehicles has been met except for the Army, Young told reporters after testifying on procurement issues before the Senate Armed Services Committee.

The Army has asked for up to 15,884 MRAP vehicles, with a near-term need of 11,953 of the vehicles.

The Defense Department plans to order about 1,600 MRAP vehicles in July for the Army, Young said

Officials plan to order about 1,600 MRAP vehicles next month, meeting the Army's near-term MRAP needs, Young said

"That has the potential to meet the lower end of the Army requirement, and so that could be the end of the program," he said.

The department has an extra $400 million that it saved by sending the vehicles downrange by ship that it could use to buy more MRAP vehicles, depending on theater requirements, Young said.

"We can make a little better than the low-end of the Army requirement, if we chose to spend the money that way," he said.

Beyond that, the department would need additional supplemental money to buy more of the vehicles because the program is funded to meet the Army's near-term need of roughly 12,000 MRAP vehicles, Young said.

Asked if the MRAP program has a future beyond filling the Army's requirement, Young said, "If we meet the MRAP requirement, yeah, we'll stop buying MRAPs."

Since May 2007, the Defense Department has made getting MRAP vehicles to troops downrange a top priority.

As of April 30, the Defense Department has ordered about 14,200 MRAP vehicles and delivered about 5,700 to the U.S. Central Command theater of operations, said Defense Department spokesman Chris Isleib.

The MRAP II vehicles being tested are meant to provide troops protection against Explosively Formed Penetrators, a particularly deadly type of roadside bomb, said Dakota Wood, an irregular-warfare expert with a nonpartisan think tank on Defense issues in Washington.

The U.S. military is likely to field blast-resistant vehicles for the foreseeable future because the roadside bomb threat is expected to persist, said Wood, of the Center for Strategic and Budgetary Assessments.

For example, the Joint Light Tactical Vehicle, which is in development, is supposed to provide the protection of an MRAP with maneuverability of a Humvee.

"All the lessons that were learned from the MRAP purchase will be applied to the JLTV," Wood said.

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