The expanding reach of China's (search) 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 (search) said Thursday.

In a speech to the Academy of Military Sciences (search), 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 Thursday speech 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 Thursday, Rumsfeld was flying to Seoul, South Korea, on the second leg of a five-nation tour.

In a report to Congress last July, the Pentagon expressed worry about China's expanding missile force.

"It is fielding more survivable missiles capable of targeting India, Russia, virtually all of the United States, and the Asia-Pacific theater as far south as Australia and New Zealand," the report said.

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.

Gen. Jing Zhiyuan, commander of the Second Artillery, which operates the country's growing arsenal of nuclear missiles, offered the assurance while hosting Rumsfeld as the first foreigner to visit his headquarters, according to two U.S. officials who participated in the meeting.

The U.S. officials briefed reporters afterward only on condition of anonymity because of the visit's sensitivity. They said Jing told Rumsfeld no foreigner had entered the command headquarters in its 39-year history. Rumsfeld signed a large, new and otherwise empty guest book.

The Chinese rejected a Rumsfeld request to visit their national military command center in the Western Hills.

Jing disavowed a recent public suggestion by another Chinese general that the United States could be targeted for a nuclear strike in the event that it intervened in a conflict over Taiwan.

Rumsfeld aides who were present during the discussions quoted Jing as saying it was "completely groundless" to say that China is targeting any country with its strategic nuclear forces.

Jing's operations chief, Senior Col. Kang Hong Gui, gave Rumsfeld a briefing, complete with Microsoft PowerPoint graphics, on the command's structure and missile forces training, without details about the numbers of Chinese missiles, some of which are capable of striking points inside the United States.

Later, in a meeting with Rumsfeld at the Great Hall of the People, President Hu Jintao said the visit to the Second Artillery headquarters and Rumsfeld's other discussions in Beijing will "help the military forces of our two countries to better enhance their mutual understanding and friendship."

Hu and Rumsfeld also discussed President Bush's planned visit to Beijing next month, and they agreed to speed up plans to increase military educational exchanges, a goal that Bush has personally endorsed.