China told the United States on Wednesday its first test flight of a stealth fighter jet should not be seen as a threat and reiterated it had no intention of challenging U.S. military might in the Pacific.

China confirmed on Tuesday it held its first test flight of the J-20 stealth fighter jet, a show of muscle during a visit by U.S. Defense Secretary Robert Gates that sought to defuse military tensions between the two powers.

The flight came against a backdrop of a massive Chinese military modernization program. China's plans to develop aircraft carriers, anti-satellite missiles and other advanced systems have alarmed neighboring countries and Washington.

China is showing off that its defenses have been strengthened to a high level, said Ahn Yinhay, a professor at Korea University in Seoul.

The United States has been ... questioning whether China is targeting the U.S., to which China is replying implicitly and explicitly that it is fully equipped with high-tech weapons.

U.S. and Chinese defense-related ships have jostled in seas near China in past years, and in 2001 a mid-air collision between a U.S. surveillance plane and a Chinese air force fighter caused a diplomatic standoff.

China has always said its military modernization is needed to protect the country's development and interests, to maintain regional stability and to upgrade sometimes woefully outdated equipment.

The People's Liberation Army has no ability, and even more than that, has no intention, to challenge America's territory and global military advantage, and does not have any aims to pursue military hegemony in the region, Rear-Admiral Yang Yi wrote in a commentary for the overseas edition of the People's Daily.

Chinese Vice Foreign Minister Cui Tiankai, speaking to reporters ahead of a state visit to the United States by President Hu Jintao next week, repeated that the test flight was not aimed at any country or to coincide with 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 Gates's visit or with China-U.S. relations, Cui said.

In Washington, Admiral Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, said he was not surprised at the development because he had long observed that China is investing in very high-end, high-tech capabilities.

The question that is always out there is to try to understand exactly why, he said, adding that the opaqueness of that, tied to our lack of a relationship, is something that I'd like to see if we can crack open.

Gates, after a visit to the arm of China's military that oversees its nuclear arsenal, sought to play down tensions between the two countries.

I think the discussions were very productive and really set the stage for taking the military-to-military relationship to the next level, he said after three days of talks with Chinese military and civilian officials.

In Taiwan, the self-ruled island China has never renounced the use of force to bring under its control, the government said the test flight constituted yet another threat to it.

China's consistent military expansion creates a threat to Taiwan's security, and we think the international community should give support to Taiwan. This would include Taiwan's ... need to purchase weapons, said Chao Chien-min, deputy chairman of Taiwan's Mainland Affairs Council.

China cut off ties with the U.S. military for most of 2010 and turned down a proposed fence-mending visit by Gates last summer, because of the Obama administration's proposed $6.4 billion arms package to Taiwan.

News of the stealth fighter's maiden flight caused national pride to swell in China. State radio said some Chinese shed tears of joy on the news, while online message boards and blogs brimmed with comments praising the aircraft.

THAT STEALTHY?

The J-20's test-flight prompted some regional analysts to reassess China's military build-up, which includes possible deployment in 2011 of the country's first aircraft carrier and a new anti-ship ballistic missile seen as a threat to U.S. aircraft carriers.

Some have said the development of the J-20 is a strong indicator China is making faster-than-expected progress in developing a rival to Lockheed Martin's F-22 Raptor, the world's only operational stealth fighter designed to evade detection by enemy radar.

If they are successful -- the stealth bomber might not be too stealthy, we have to find out -- it will definitely make it more difficult for United States carriers and long-range assets to operate in this region, said Narushige Michishita of Tokyo's National Graduate Institute for Policy Studies.

U.S. analyst Dean Cheng of the Heritage Foundation said it was likely that the system has not reached large-scale production, much less initial operational capability.

But he said the test-flight should serve as a reminder to both Taipei and Washington of the evolving situation in the air.

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