US Defence Secretary Donald Rumsfeld has called on China to provide wary neighbours with a clear explanation of its missile build-up.
Speaking on the final day of a visit to Beijing, Mr Rumsfeld told Chinese strategic experts at the Academy of Military Science that the Pentagon believed China was expanding the reach of its arsenal of ballistic missiles to cover most of the world.
"Those advances in China's strategic strike capability give cause for concern, particularly when there is an imperfect understanding among others about such developments," Mr Rumsfeld said.
"As a result, a number of countries with interests in the region are asking questions about China's intentions," he added, reiterating his main theme during two days of meetings in Beijing with military and political leaders of the rising Asian power.
Chinese Foreign Ministry spokesman Kong Quan defended China's military expansion. "It's right for China to enhance its justified defence capabilities," he said.
A report issued by the Pentagon in July suggested China's military spending was poised to increase rapidly as China's economy continued to grow at a breakneck pace.
The report said China added about 100 missiles a year to the arsenal of 650-730 short-range missiles pointed at rival Taiwan and was fielding missiles capable of reaching nearly all of the United States, as well as Russia, India and Australia.