The US Air Force unit that oversees a remote Cold War-era nuclear missile installation has failed a safety test, the Air Force has said.
The 341st Missile Wing at Malmstrom Air Force Base in Montana made "tactical-level errors" in an exercise, it said.
The exercise concluded on Tuesday was meant to test the unit's ability to operate safely, the Air Force said. But a senior Air Force commander said the failure did not indicate the US nuclear arsenal was at risk.
"These inspections are designed to be tough to pass," Lt Gen James Kowalski said in a statement. "A failure doesn't mean the wing isn't able to accomplish its mission."
On Tuesday, the Air Force revealed the 341st Missile Wing was rated "unsatisfactory" after making errors during exercises conducted during an inspection 5-13 August. As a result of the failure, the entire inspection was graded "unsatisfactory".