The US nuclear force is plagued by declining morale, manpower shortages and mismanagement that could jeopardize its safety and effectiveness, Defense Secretary Chuck Hagel said Friday.

The Pentagon chief cited sobering results from two reviews and said the military had neglected the nuclear arsenal as it had been preoccupied with wars in Iraq and Afghanistan over the past decade.

Reviews ordered by the Pentagon "found evidence of systematic problems that if not addressed could undermine the safety, security and effectiveness of elements of the force in the future," Hagel told reporters.

The findings showed "a consistent lack of investment and support for our nuclear forces over far too many years has left us with too little margin to cope with mounting stresses," he said.

The inquiries urged an end to excessive bureaucracy and "a culture of micromanagement" marked by petty inspections, officials said.

Hagel unveiled an "action plan" that calls for making the nuclear force a higher priority, reorganizing the command, reassuring troops of the importance of the mission and boosting funding and personnel.

The moves came after a series of embarrassing revelations about the state of the nuclear force and land-based missiles in particular, with dozens of airmen caught cheating on a proficiency test for overseeing intercontinental ballistic missiles.

A number of senior nuclear commanders also were disciplined for personal misconduct, with the general in charge of the ICBM force sacked after he went on a drunken bender during a trip to Russia.

- Only one wrench -

Hagel said troops who work with nuclear weapons are worried they have no career prospects in a military that often seems indifferent to their mission.

"The root cause has been a lack of sustained focus, attention and resources resulting in a pervasive sense that a career in the nuclear enterprise offers too few opportunities for growth and advancement," he said.

To boost morale, the US Air Force is giving a raise to ICBM crews and issuing a new medal to recognize excellence in "nuclear deterrence operations," officials said.

Reflecting the troubled state of the force, the reviews pointed to a wrench needed to install a nuclear warhead on the tip of a Minuteman missile. The wrench was in a toolkit shared by all three ICBM bases in North Dakota, Montana and Wyoming. And when one crew needed the wrench, it was shipped from another base by Federal Express.

The crews were "creative" in solving the problem, "but that's not the way to do it," said Hagel, adding each base now had their own sets of tools.

The Pentagon planned to ask for a ten percent annual increase in funding for the nuclear force over the next five years, which would come to about $1.5 billion a year, Hagel said.

"We will need to make billions of dollars of additional investments in the nuclear enterprise over the next five years," he said.

Most of the recent scandals have been centered on the land-based missiles maintained by Air Force crews, though the Navy also had a cheating scandal among sailors who work on submarines armed with nuclear missiles.

Hagel has granted permission to the Navy to hire more civilians to help maintain its nuclear-armed submarines and the Air Force planned to add about 1,100 troops and civilians to its nuclear command to fill manpower gaps, the Pentagon said.

- 'Taking it for granted' -

Concerns about slipping standards in the nuclear force since the end of the Cold War are not new, and Hagel's predecessor, Robert Gates, ordered a review in 2008 that came to similar conclusions.

Asked why the problems had been allowed to fester, Hagel said the Pentagon had been focused on "two large ground wars" in Iraq and Afghanistan and the country had become complacent about the role of the destructive weapons.

"I think there's been, nationally, a sense of just taking it for granted. So what? There's not going to be a nuclear exchange," he said. "We just have kind of taken our eye off the ball here."

Hagel was due to travel Friday to Minot Air Force Base in North Dakota, where airmen oversee intercontinental nuclear missiles and bomber aircraft.

Arms control advocates argue morale problems are inevitable because the crews sense their mission has become obsolete with the collapse of the Soviet Union and that it is time to scale back the costly arsenal.