WASHINGTON (AP) — Defense Secretary Chuck Hagel said Friday there is “no room for error” by those responsible for America’s nuclear forces, commenting publicly for the first time on what he called “troubling lapses” in professionalism within the nuclear ranks.

Speaking at the headquarters of the military’s nuclear war-fighting command in Omaha, Neb., Hagel alluded to a series of missteps revealed in recent months by The Associated Press, including lapses among those who operate and support the Air Force’s nuclear missile force. Last month, two senior nuclear commanders were fired amid misconduct investigations, and in August, service members working at a nuclear-missile base in Montana failed a safety and security inspection.