The Army’s plan for a four-year shutdown of its main battle tank production line is based on a careful risk analysis,  top service officials said yesterday in response to questions from Senators.

Temporarily shutting down the General Dynamics [GD] Land Systems (GDLS) tank plant where the M1 Abrams tank is built is a plan based on a “clear business case,” Army Secretary John McHugh said yesterday during a hearing of the Senate Defense Appropriations Subcommittee. McHugh said the Abrams fleet is “the most modern” of the Army’s current major equipment and that its acquisition objective has been met for the time being.

“The cost of shutting down and mothballing the plant, including the cost of rebuilding the employee base, was far more economically sensible than maintaining the minimum production necessary through the period until we begin to develop a follow-on to the Abrams platform,” he said.

“The decision on the future production of the tank was simply made on the business case,” he added. “The business case was clear.”

Members of the House of Representatives earlier this month sent a letter to McHugh urging the continuation of the Abrams production line based in Lima, Ohio. Rep. Sander Levin (D-Mich.), along with nearly a third of the House membership, is challenging the ArmyÂ’s plan.

The letter, initiated by Levin and Rep. Mike Rogers (R-Ala.), warns McHugh that the pause “could end up costing more in the long run and result in lost capacity and readiness.” They question the Army’s risk analysis.

“The cost of shutdown and restart of Abrams tank production appears to be more than the cost of continued limited production,” the letter states. “Instead of reconstituting this vital manufacturing capability at a higher cost, it would seem prudent to invest these select resources in continued Abrams production.”

The House Armed Services Committee, during its markup of the 2012 Defense Authorization bill, added $425 million to continue the production line for the M1 Abrams tanks and M2 Bradley fighting vehicles. Bradley’s are produced by BAE Systems.

GDLS is based in Sterling Heights, Mich., and is at the core of the state’s defense industrial base.

The Army wants to stop Abrams production in 2013 and restart it again in 2017. This would be the first U.S. tank-production break since 1941.

McHugh said the Army is “working closely” with the Pentagon’s chief weapons buyer, Ashton Carter, to devise ways” to help preserve that expert force.

“We recognize it and value it,” he added.