Lockheed Martin, the world’s largest defense contractor, said Tuesday that it is protesting the award of a major contract to build the next-generation of ground vehicles, a deal worth up to $30 billion.

The announcement comes about two weeks after the Army awarded the contract to build what’s known as the Joint Light Tactical Vehicle to Oshkosh Defense.

AM General, which also lost out on the contract, said on Tuesday that it would not protest the decision.

The contract to build as many as 55,000 of the vehicles is one of the largest contracts awarded by the Army in years. With work expected to last through 2040, the competition was particularly stiff, and Lockheed’s announcement shows that as defense spending tightens, contractors are willing to fight fiercely for work, especially with so much at stake.

“We firmly believe we offered the most capable and affordable solution for the program,” the Bethesda-based company said in a statement. “Lockheed Martin does not take protests lightly, but we are protesting to address our concerns regarding the evaluation of Lockheed Martin’s offer.”

It declined to elaborate further.

While the JLTV would have the agility of the Humvee, able to ford rivers and cruise off-road, it would also be heavily armored and able to withstand the kinds of blasts that took so many lives in Iraq and Afghanistan.

The initial contract awarded last month was for $6.7 billion for 17,000 vehicles. Production is slated to begin in the first quarter of fiscal 2016, and the Army would have its first unit equipped with the vehicles in 2018.