Key defense contractors said Monday that automatic federal spending cuts set to begin next month would hamstring their ability to develop critical machinery, equip military personnel and help maintain national security.

David Langstaff, president and chief executive officer of TASC Inc., said it would be “irresponsible” to allow the spending cuts, known as sequestration, to take effect Jan. 2.

“Sequestration … will shatter our ability to execute the U.S. national security strategy,” Mr. Langstaff said during a panel discussion with three other defense industry CEOs at the National Press Club.

The defense contractors urged lawmakers to reach an agreement on a framework to avert sequestration, which would cut $1.2 trillion from the federal budget over the next decade. The Defense Department would lose $500 billion over that period, beginning with a more than $50 billion cut to its 2013 budget.