China said it had tested "a new spacecraft, not a missile" in August that could reach five times the speed of sound, contradicting a recent report in the Financial Times newspaper.
Chinese Foreign Ministry spokesman Zhao Lijian said the new technology would be used for "the benefit of mankind" in answer to reporters' questions.
The US raised concern over China's growing technological progress and its inability to defend against the hypersonic threat.
What did China say?
Lijian said the launch of the hypersonic spacecraft was a "routine test" reusing old technology to reduce costs.
He said the test was of "great significance for reducing the use-cost of spacecraft and could provide a convenient and affordable way to make a round trip for mankind's peaceful use of space."
The launch was conducted by the military that runs China's space program.
"China will work together with other countries in the world for the peaceful use of space and the benefit of mankind," Zhao added.
The remains of the launch fell into the East China Sea.
Zhao's comments come after China fired three astronauts into orbit for a six-month mission aboard its space station on Saturday.
How has the US reacted?
"We have concerns about what China is doing on hypersonic," US disarmament ambassador Robert Wood told reporters in Geneva.
"We just don't know how we can defend against that type of technology, neither does China or Russia," he said
US Defense Secretary Lloyd Austin said earlier Washington was closely watching new Chinese weapons systems, but did not comment on the hypersonic launch.
But US Congressman Mike Gallagher, a Republican, had very real concerns over the launch.
"This test should serve as a call to action. If we stick to our current complacent course, or place our hopes in bankrupt buzzwords like 'integrated deterrence,' we will lose the new Cold War with Communist China within the decade," said Gallagher.
What did the FT report suggest?
The Financial Times claimed Saturday that the hypersonic "missile" had gone around the world in low orbit before missing its intended target.
Citing several sources, the report suggested the West was underestimating Chinese technology, which now had the possibility of launching a "harder to track" nuclear attack on the US that could evade missile defense systems.
Both the US and Russia are currently developing hypersonic missiles.
Japanese Chief Cabinet Secretary Hirokazu Matsuno on Monday said his country would step up its detection, tracking and elimination capability of "any aerial threat."
"China's rapidly expanding and increased military activity at sea and airspace has become a strong security concern for the region including Japan and the international society," Matsuno said.
