China has told the United States its first test-flight of a stealth fighter should not be seen as a threat.
The communist state says it has no intention of challenging the US military might in the Pacific.
The J-20 flight comes amid a major Chinese military modernisation programme which includes plans to develop aircraft carriers, anti-satelitte missiles and other advanced systems.
US Defense Secretary Robert Gates is visiting China in a bid to defuse military tensions between the two powers.
China's Vice Foreign Minister Cui Tiankai said the test flight was not aimed at any country or to coincide with Mr Gates' visit: "No other country has reason to feel worried or troubled about this. What you've raised (about the stealth flight) had nothing to do with Defense Secretary Mr Gates' visit or with China-US relations," Cui said.
China has always said its military modernisation is needed to protect the country's development and interests, to maintain regional stability as well as to upgrade sometimes woefully outdated equipment.