Specialty truck builder Oshkosh has secured a huge deal to build the United States Army's next-generation family of medium tactical vehicles (FMTV) A2 variants.

The Pentagon says that the seven-year supply deal, reportedly for up to 2400 trucks, is worth at least $US476million.

The deal, won by Oshkosh against rival AM General, repeats its 2009 contract to build the first generation of the FMTVs for the US Army, which owns the design and technical data package for the trucks and trailers.

The Army says that FMTVs have "formed the backbone of the Army's local, linehaul, and unit resupply missions in combat, combat support, and combat service support units" for decades.

They comprise 15 variants, which share a common chassis and components and are used as a variety of weapon, sensor and communication platforms.

Oshkosh, which has built over 150,000 defence vehicles for the US, has delivered over 36,000 FMTV trucks and trailers.

The Army says that a redesign was called-for because in recent conflicts, it has added more protection to the FMTVs – thus adding weight. New high-tech systems installed also require more power.

"That gave the crew the protection they needed and kept them connected to modern battlefield technology, but it also took away from how the vehicles were originally intended to perform."

Oshkosh won a deal in 2015 to build the Army's Humvee replacement, the joint light tactical vehicle (JLTV) – reckoned to initially be worth $US6.7billion…and possibly as much as $30bn.