Beijing ? The expanding reach of China’s nuclear missiles is worrisome to the United States, which would like Chinese officials to be more open about their intentions, Defense Secretary Donald H. Rumsfeld said today.

In a speech to the Academy of Military Sciences, Rumsfeld said nuclear capability is an area in which the United States would like China to show more transparency.

“China … is expanding its missile forces and enabling those forces to reach many areas of the world well beyond the Pacific region,” Rumsfeld said. “Those advances in China’s strategic strike capacity raise questions, particularly when there’s an imperfect understanding of such developments on the part of others.”

His statement echoed a theme he has pressed during his first visit to China since becoming defense secretary in 2001 – that China’s secretiveness creates international worries about its military intentions.

He told a small group of students and faculty members at the Central Party School on Wednesday that “growth in China’s power projection understandably leads other nations to question intentions and to adjust their behavior in some fashion.”

In his speech today to the Academy of Military Sciences, Rumsfeld said many countries with an interest in the Asia-Pacific region are questioning China’s military intentions.

While it is up to China to decide how much it wishes to say on the subject, “greater clarity would generate more certainty in the region,” Rumsfeld said. He made plain that the United States is not opposed to China’s efforts to improve the training and equipping of its already large military.

Modernization is appropriate as long as it is transparent, he said.

Later today, Rumsfeld was flying to Seoul, South Korea, on the second leg of a five-nation tour.

On Wednesday, the commander of China’s nuclear missile forces reaffirmed to Rumsfeld that in an armed conflict China would not be the first to use nuclear weapons.