WASHINGTON (AFP) - The US military has suspended 34 officers in charge of launching nuclear missiles for cheating on a proficiency test, Air Force leaders said on Wednesday, Jan 15, 2014.

The scandal at Malmstrom Air Force Base in Montana marked the latest in a series of damaging revelations dogging the country's nuclear force, including a separate probe into illegal drugs that came to light last week.

"There was cheating that took place with respect to this particular test," Air Force Secretary Deborah Lee James told a news conference.

"Some officers did it. Others apparently knew about it, and it appears that they did nothing, or at least not enough, to stop it or to report it."

She called the cheating "absolutely unacceptable behaviour" but insisted the scandal did not call into question the safety or competence of the nuclear force.

"And very importantly, I want you to know that this was a failure of some of our airmen. It was not a failure of the nuclear mission," said Ms James.

The launch officers tied to the cheating allegations have also lost their security clearances.

The cheating came to light as investigators were looking into suspicions of illicit drug possession by some officers at Malmstrom and other bases.

Two of the officers implicated in the cheating also are linked to the separate drug case, which involves officers at other bases, officials said.

The Air Force has come under growing scrutiny over a spate of embarrassing setbacks linked to the nuclear force, amid persistent reports of low morale among the troops assigned to the mission.

All launch officers in the missile force have been ordered to take the proficiency exam again and the testing will be completed by Thursday, said Ms James, who was accompanied by the Air Force chief of staff, General Mark Welsh.

The Malmstrom base has a total of about 190 launch officers, including the 34 who have been suspended.