The test comes amid the ongoing tensions between the US and North Korea
The US military has carried out the first test of a missile defence system designed to stop an intercontinental ballistic missile (ICBM).
It was not immediately clear if the test of the Ground Based Midcourse Defense (GMD) system at Vandenberg Air Force Base in California was successful.
Pentagon officials said the test was to simulate the capability for responding to a hypothetical North Korean ICBM.
The ICBM was launched from a site on the Marshall Islands in the Pacific, and was equipped with a warhead which would approximate the qualities of a nuclear warhead.
The GMD interceptors carry no warheads themselves but rely on the kinetic energy of their impact to destroy the incoming missile.
Kinetic energy hits are intended to minimise the risk of detonating conventional warheads, including nuclear tipped ballistic missiles.
It is a similar missile defence system to the Terminal High Altitude Area Defence (THAAD) system, which was recently deployed in South Korea.
North Korea's ballistic missile tests have created tensions between Pyongyang and Washington, with Kim Jong Un featuring commonly in discussions between President Donald Trump and Chinese counterpart Xi Jinping.
Despite UN and unilateral sanctions, North Korea has continued with its missile tests. It has argued the sanctions are an infringement of its right to self-defence.
Its most recent test of a medium-range Scud missile was claimed as a success, although North Korea's ability to launch a ballistic missile capable of hitting intercontinental targets has been disputed.
The state has stressed that it will continue to develop a pre-emptive strike capability.
Speaking ahead of today's test, US Navy Captain Jeff Davis said: "[North Korea continues] to conduct test launches, as we saw even this weekend, while also using dangerous rhetoric that suggests that they would strike the United States homeland."