(Recasts with comments from officials, background)
By Phil Stewart and David Alexander
WASHINGTON, Jan 30 (Reuters) - Just over half of the 183 nuclear missile launch officers at Malmstrom Air Force Base in Montana have been implicated in a widening exam cheating scandal, the Air Force said on Thursday, acknowledging it had "systemic" problem within its ranks.
The cheating was discovered during an investigation into illegal drug possession among airmen, when test answers were found in a text message on one missile launch officer's cell phone. The Air Force initially said 34 officers either knew about the cheating or cheated themselves.
But Air Force Secretary Deborah Lee James told a Pentagon news conference on Thursday that the total number of implicated officers had grown to 92, all of them at Malmstrom, one of three nuclear missile wings overseeing America's 450 inter-continental missiles, or ICBMs.
"I believe now that we do have systemic problems within the force," James said. "We do have systemic issues out there and we need to address this holistically.
James expressed confidence in the safety of America's nuclear arsenal, despite the scandal, saying there were multiple checks to ensure nuclear launch officers knew how to do their jobs. She said the entire force had been re-tested.
But she also said all 92 implicated officers had been decertified and pulled from their missile duties. The Air Force said that meant remaining launch officers were doing extra shifts, and officers with the missile launch backgrounds were being pulled from other assignments to supplement the force.
"I'll tell you right up front, there's been no operational impact and we do not see an operational impact in the mission at Malmstrom Air Force Base," Lieutenant General Stephen Wilson, the head of the Air Force's Global Strike Command.
Officials said they did not believe the cheating extended to the other missile wings since the tests at each base were different, meaning answers cannot be shared between bases.
The scandal is the largest single case of cheating in recent memory in America's nuclear missile forces, which are struggling with questions about discipline and morale in the post-Cold War era, when other missions, including the wars in Afghanistan and Iraq, garner more attention and resources.
But the exam cheating is only the latest embarrassment for the nuclear force. James acknowledged on Tuesday that 13 airmen were under investigation for illegal drug possession, up from 11. That includes three nuclear missile launch officers.
The head of the U.S. intercontinental ballistic missile force, Air Force Major General Michael Carey, was fired in October for getting drunk and carousing with women while leading a government delegation to Moscow for talks on nuclear security.
According to an investigation by the Inspector General of the Air Force, Carey was at one point said to be slurring his words on a delegation trip to a local monastery and asked repeatedly for a chance to sing with a Beatles cover band at a Mexican restaurant.
The cheating scandal itself is an early test for James, who last year became the second woman to take over the Air Force's top civilian job. She has so far seized the issue, addressing the Pentagon media twice on the matter this month, and committing to handle the matter transparently.
James, who visited the nuclear missile wings last week, has said over the past two days that the problems within the nuclear missile force were in part cultural, with airmen not "wanting to report on their buddies."
Beyond a lack of integrity and poor judgment among airmen, she has also blamed the decision to cheat on a test-driven culture within the nuclear force, which must consistently score a passing grade of at least 90 percent correct on exams.
"I heard repeatedly from teammates that the need for perfection has created a climate of undue stress and fear. Fear about the future. Fear about promotions. Fear about what will happen to them in their careers," she added. (Reporting by Phil Stewart; Editing by Chizu Nomiyama)