The US Air Force said on Monday it had conducted a successful test of a hypersonic weapon, which flew at five times the speed of sound.
The test was conducted on Saturday off the coast of Southern California when a B-52 bomber released an Air-launched Rapid Response Weapon (ARRW), the Air Force said in a statement.
"Following separation from the aircraft, the ARRW's booster ignited and burned for the expected duration, achieving hypersonic speeds five times greater than the speed of sound," it said.
The United States is not alone in developing hypersonic weapons, whose speed and manoeuvrability make them difficult to track and intercept.
Russia has fired hypersonic missiles at targets in Ukraine and China has tested hypersonic weapons, US military officials have said. China's foreign ministry denied in October that it had conducted a weapons test.