In a speech today at the Central Party School in Beijing, Rumsfeld said China is being secretive about what the U.S. characterizes as a considerable buildup in its military capabilities.
He called for Beijing to be more transparent about its military affairs.
"A growth in China's power projection understandably leads other nations to question [China's] intentions and to adjust their behavior in some fashion," Rumsfeld said. "The rapid -- and, from our perspective at least, nontransparent -- nature of this buildup contributes to their uncertainty."
Rumsfeld's visit comes at a moment when China has just demonstrated its growing technological prowess by successfully completing its second manned space mission.
The mission had no known military applications, but it was a powerful demonstration of China's control of dual-use technology. Coupled with its grasp of atomic physics, and its massive economic growth, that makes China's intentions a concern for its neighbors, particularly U.S. allies Japan and South Korea.
Hence Rumsfeld's desire for demystification of China's intentions. At a joint press conference today with his Chinese counterpart Cao Gangchuan, the U.S. defense secretary offered openness on the part of the United States.
"I sense a desire on the part of the [Chinese defense] minister and his team to do essentially that which those of us in the United States defense ministry want to do, and that is to find activities and ways that we can work with each other that will contribute to demystifying what we see of them and what they see of us," Rumsfeld said.
At the press conference, Cao denied there had been any big increase in China's defense spending. The country's top priority, he said, is to develop the economy and raise living standards.
Cao added that China, in any event, could not afford to raise defense spending by much, and he said the "true" military budget this year is some $30 billion. That is just a fraction of the U.S. military budget of almost $500 billion.
However, the budget figure given by Cao has been met with skepticism by some Western analysts, including London-based Independent military consultant Alexandra Ashbourne.
"That strikes me as surprisingly low, and I would be very cautious about the credibility of that figure," Ashbourne said.
She noted that even a small country like Britain spends some $40 billion on defense -- $10 billion more than China purports to be spending.
Ashbourne said China does indeed seem to be quietly improving its armed forces, but she suggests this should likely be seen as an upgrading of capabilities rather than a numerical expansion.
"It's indeed being kept very quiet, but the Chinese have clearly expressed a lot of interest in Western technology, and they are clearly looking to grow their armed forces," Ashbourne said. "China is not traditionally an expansionist country, it has very much stayed within its own borders, but it does seem to be clear that they are looking to modernize and upgrade what was a fairly low-tech capability."
She said East and Southeast Asia are areas where defense spending is "quite high." China, she said, can justify its own modernization by comparing itself to neighbors like Japan, South Korea, and Malaysia, which all have modern armed forces.
In his talk to young officials at the Central Party School, the Chinese Communist Party's top training center, Rumsfeld also touched on the U.S. military presence in Central Asia.
The Reuters news agency reported that Rumsfeld complained that the Shanghai Cooperation Organization, which groups most of the Central Asian states with Russia and China, had sought to have the U.S. military ousted from Uzbekistan. Uzbek authorities have asked U.S. forces to leave following Washington's criticism of Uzbekistan's human rights record.
The Shanghai group in July issued a communique calling on Washington to wind down its military presence in Central Asia.