WASHINGTON (AP) — Defense Secretary Chuck Hagel is commenting publicly for the first time on what he calls "troubling lapses" of professionalism within the ranks of U.S. nuclear forces.

Hagel alludes to a series of missteps revealed by The Associated Press among those who work with the Air Force's nuclear missile force, including a failed inspection. Two senior nuclear commanders were fired amid misconduct investigations.

Hagel is speaking Friday at the headquarters of the military's nuclear war-fighting command in Omaha, Neb.

In prepared remarks, Hagel says the failures had been exposed by what he called "close scrutiny" and the Pentagon's most rigorous evaluations.

Hagel says the nuclear weapons force has "no room for error." He praises the retiring head of the command for enforcing tough standards.