The United States on Tuesday successfully tested an unarmed Minuteman III intercontinental ballistic missile (ICBM) in a launch directed from an airborne command center, the Air Force said.

The missile was launched at 12:21 am (0721 GMT) from Vandenberg Air Force Base in California, travelling 6,700 kilometers (4,200 miles) over the Pacific Ocean before landing in the sea near the Marshall Islands.

"The test demonstrates that the United States' nuclear deterrent is safe, secure, reliable and effective," the Air Force said in a statement.

"Airmen... were aboard the US Navy E-6 aircraft to demonstrate the reliability and effectiveness" of the airborne launch control system, it said.

Colonel Omar Colbert, commander of 576th Flight Test Squadron, said "the Minuteman III is 50 years old, and continued test launches are essential."

"This visible message of national security serves to assure our allies and dissuade potential aggressors," he said.

The Air Force added that test launches were "not a response or reaction to world events or regional tensions."

The Minuteman III has been the only surface-to-air missile in the US nuclear arsenal since 2005. It is installed at bases in Wyoming, North Dakota and Montana.

Trident nuclear missiles are deployed on US submarines, and US strategic bombers also carry nuclear devices.