The US military announced Tuesday a new test of a hypersonic missile, as Pentagon officials seek to match or get ahead of China's and Russia's advances in the cutting-edge strategic weapons technology.
The Defense Advanced Research Projects Agency (DARPA) said it had recently completed a free flight test of an aircraft-launched hypersonic missile that maintained a speed of more than Mach 5, or five times the speed of sound (at least 3,800 miles per hour, or 6,100 kilometers per hour).
The missile flew to an altitude greater than 65,000 feet (19,800 meters) and soared over 300 nautical miles, said DARPA, the Pentagon's high-tech research body.
It was the second test under the agency's HAWC Program - named for hypersonic air-breathing weapon concept - and the missile had a different configuration from the first, which was tested last September.
According to CNN, the newest test took place in mid-March but was kept quiet to avoid appearing to escalate the geopolitical tensions surrounding the Russian attack of Ukraine.
In March 2020, the US army and navy undertook a joint test of a different hypersonic prototype.
DARPA said air-breathing hypersonic missiles use air captured from the atmosphere to help sustain propulsion.
"This Lockheed Martin HAWC flight test successfully demonstrated a second design that will allow our warfighters to competitively select the right capabilities to dominate the battlefield," said Andrew Knoedler, HAWC program manager, in a statement.
Hypersonic missiles pose a potential threat to the global military balance, capable of being steered to deliver nuclear weapons precisely on target, at speeds too fast to intercept.
The Pentagon is under pressure to match China's apparent successful test of a hypersonic missile last year that flew around the globe and hit a target in China.
Russia also claimed two weeks ago to have fired two hypersonic missiles in strikes on Ukraine.
The three countries said the joint initiatives will bolster existing efforts to deepen cooperation in numerous areas that they already agreed when forming the new defensive pact last September.
"We... committed today to commence new trilateral cooperation on hypersonics and counter-hypersonics, and electronic warfare capabilities, as well as to expand information sharing and to deepen cooperation on defence innovation," they said in a joint statement.
"These initiatives will add to our existing efforts to deepen cooperation on cyber capabilities, artificial intelligence, quantum technologies, and additional undersea capabilities.
"As our work progresses on these and other critical defense and security capabilities, we will seek opportunities to engage allies and close partners."
Russia, China, the United States and North Korea have all test-launched hypersonic missiles, with Tuesday's announcement coming just weeks after Moscow said it had launched them for the first time in its war in Ukraine.
Hypersonic missiles, like traditional ballistic missiles which can deliver nuclear weapons, can fly at more than five times the speed of sound.
While ballistic missiles fly high into space in an arc to reach their target, a hypersonic weapon flies on a trajectory low in the atmosphere, potentially reaching a target more quickly.
Crucially, a hypersonic missile is manoeuvrable - like the much slower, often subsonic cruise missile - making it much harder to track and defend against.
Russia is seen as the most advanced nation in this field, while China is also aggressively developing the technology, according to the US Congressional Research Service (CRS).
France, Germany, Australia, India and Japan have been working on hypersonics, and Iran, Israel and South Korea have conducted basic research on the technology, the CRS has previously said.
The US, Britain and Australia launched their landmark security pact last September, alongside Canberra scrapping a multi-billion-dollar submarine deal with France that infuriated Paris.
The pact, known as AUKUS, was proclaimed at the time as allowing the three allies to share advanced technologies.