The US Air Force is preparing to test an unarmed Minuteman 3 intercontinental ballistic missile (ICBM) with a launch from California, the fourth such test this year. <br/><br/>The 30th Space Wing says the missile is to be launched tomorrow from Vandenberg Air Force Base. An Air Force statement said, the test would show the effectiveness, readiness, and accuracy of the weapon system. <br/><br/>Minuteman missiles are regularly tested with launches from Vandenberg that send unarmed re-entry vehicles 6,800 kilometers across the Pacific. However, the latest US launches come amid tensions with North Korea as that nation develops its own ICBMs.<br/><br/>