BEIJING, Oct. 20 - Defense Secretary Donald H. Rumsfeld concluded a visit to Beijing today with an unusual round-table session with Chinese officers that turned into a lively, but never hostile, discussion about the two countries" military capabilities and intentions.

Mr. Rumsfeld told students and faculty members at the Academy of Military Sciences here that China"s neighbors worry about Beijing"s decision to expand its missile forces, and to increase the range of those rockets so they can strike nations beyond the Pacific.

He stressed that while China may make sovereign decisions about its military policy, other nations have the right to question whether it is being forthright in the level of its spending on troops and weapons, and the motivation driving its growing arsenal.

In particular, the defense secretary questioned why China and Russia had joined diplomatic forces in an effort to prompt Central Asian states, especially Uzbekistan and Kyrgyzstan, to evict American and coalition forces from bases on their soil.

Those American and allied troops and aircraft still are required to combat Taliban and Al Qaeda forces attempting to undermine Afghanistan"s new government, and for continued relief efforts there, Mr. Rumsfeld said. And he stressed that the United States has no intentions of establishing large permanent bases in those former Soviet states.

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

One Chinese officer rebuffed Mr. Rumsfeld"s critique that Beijing"s military budget remains a mystery, saying that increases were required to modernize Chinese forces after years of inadequate spending.

And another officer said that while Mr. Rumsfeld accused the Chinese of sending mixed signals about its global intentions, the United States had not been transparent in its reasons for securing access rights to the base in Uzbekistan, nor in stating how long American forces planned to stay in Central Asia.

American reporters traveling with Mr. Rumsfeld were allowed to hear the defense secretary"s opening remarks and the first question posed by a Chinese officer, but were required by the academy"s leadership to leave for the remainder of the 45-minute discussion.

Details of the rest of the give-and-take were supplied by Lawrence Di Rita, Mr. Rumsfeld"s spokesman, who attended the entire session. Mr. Di Rita described the face-to-face session between Mr. Rumsfeld and the Chinese officers as "extremely professional," and he said it had allowed each side to gain greater understanding of the other.

On Friday, Mr. Rumsfeld is scheduled to attend security consultations in Seoul, South Korea, where command arrangements for the combined American-South Korean force are expected to be discussed.

Under current agreements, the South Korean armed forces are under South Korean command during peacetime, but fall under American command in case of war. South Korean leaders have expressed a desire for that agreement to be reviewed, with a goal to retaining command of their forces at all times.

Gen. Leon J. LaPorte, the commander of American forces in South Korea, said Seoul"s desires reflected "a natural evolution," but that no decisions had been made.

He stressed that the United States and South Korea had maintained mutually beneficial relations for a half-century and that, today, "It"s natural for them to say, listen, we appreciate the support we received. We are now capable of doing more things and taking a more predominant role."

General LaPorte said provocative incidents by North Korea along the demilitarized zone and in border waters had significantly declined over the past year. He also described the remarkable increase in the number of South Koreans visiting North Korea - including 40,000 South Koreans who crossed the demilitarized zone in August for tourism or business.