The US Air Force on Friday sacked the two-star general in charge of the country's nuclear missile arsenal after an investigation revealed alleged "personal misbehavior."

Major General Michael Carey was relieved of his command of the 20th Air Force, responsible for maintaining "on-alert" intercontinental ballistic missiles, because of "a loss of trust and confidence in his leadership and judgment," spokesman General Les Kodlick told reporters.

Carey is the second senior officer in the nuclear command to be fired this week. The deputy commander of the country's nuclear forces, Vice Admiral Tim Giardina, was sacked two days ago after he came under investigation for allegedly using counterfeit chips at a casino in Iowa.

Friday's decision was taken by the head of Global Strike Command, Lieutenant General James Kowalski, who had ordered an Air Force inspector general investigation several months ago after receiving "reports of misbehavior" by Carey, Kodlick said.

The spokesman would not reveal the nature of the misbehavior pending the outcome of the investigation but said it did not involve sexual misconduct or criminal activity.

The misbehavior occurred during a work trip but officials would not provide further details.

However, a defense official, speaking on condition of anonymity, told AFP the misbehavior was "alcohol-related."

Officers said Carey was not being sacked for any conduct related to the readiness of the 20th Air Force unit at F.E. Warren Air Force base in Wyoming or to recent failed inspections for some missile units.

"20th AF continues to execute its mission of around-the-clock nuclear deterrence in a safe, secure and effective manner," Kowalski said in a statement.

"It's unfortunate I've had to relieve an officer who has had an otherwise distinctive career spanning 35 years of commendable service," he said.

The vice commander of Air Force Global Strike Command, Major General Jack Weinstein, was named as the interim commander of the 20th Air Force unit.

The military's nuclear command has come under growing scrutiny in recent years after a number of blunders and critical inspections.

The nuclear missile unit at Minot Air Force Base in North Dakota earlier this year disciplined 17 launch control officers after an inspection uncovered problems and later relieved an officer who oversees training.

In August, a missile unit in Montana failed a nuclear safety and security inspection.

In 2008, then defense secretary Robert Gates sacked the Air Force secretary and chief of staff, blaming them for what he called an erosion of standards that led to two mistakes involving nuclear weapons.