ZHUHAI, China - China is leading the U.S. in a race to deploy hypersonic missiles that would defeat existing air defense systems, according to senior U.S. officials.The combination of speed, maneuverability and altitude of these missiles makes them difficult to track and intercept. They travel at speeds of more than five times the speed of sound or about 6,200 kilometers (3,853 miles) per hour. Some will travel as fast as 25,000 kilometers per hour, according to U.S. and other Western weapons researchers. That's about 25 times as fast as modern passenger jets.Admiral Harry Harris, the former head of U.S. Pacific Command, told the House Armed Services Committee in February last year that hypersonic weapons were one of a range of advanced technologies where China was beginning to outpace the U.S. military, challenging its dominance in the Asia-Pacific region.Last April, Michael Griffin, the U.S. Undersecretary of Defense for Research and Engineering, told the Senate Armed Services Committee that China has deployed, or is close to deploying, hypersonic systems armed with conventional warheads. These can travel thousands of kilometers from the Chinese coast and threaten American forward bases or carrier battle groups, he said."We do not have defenses against those systems," Griffin said.Russia may have already fielded a hypersonic weapon. At a parade in May last year, the Russian military displayed what it had earlier said was a hypersonic missile. Russian President Vladimir Putin has described the missile as invincible.Russia's defense ministry did not respond to questions from Reuters about its hypersonic weapons capabilities.