U.S. Defense Secretary Chuck Hagel is ordering top military officials to review the nation's nuclear force after alleged drug possession and cheating by Air Force officers.
The Pentagon says Hagel is also calling for an independent review.
Rear Admiral John Kirby, a Pentagon spokesman, says Hagel believes it is time to put renewed emphasis on examining the health of the nuclear force, and particularly those issues that affect morale, professionalism, performance and leadership of the people who make up that force.
Kirby says the secretary makes it clear that there is no mission more vital to national security than strategic nuclear deterrence.
Last week, the Air Force suspended 34 officers in charge of launching nuclear missiles for allegedly cheating or tolerating cheating on a proficiency test.
The alleged cheating was discovered during a separate investigation into charges of drug possession by officers at a Montana air force base.
There have also been reports of low morale and boredom among airmen and an Air Force general was fired last year for getting drunk while in Russia for a nuclear exercise.