The United States last year urged China to become a responsible stakeholder in the international system. On Thursday, Thomas Christensen, the new deputy assistant secretary of state for East Asian and Pacific affairs, described himself as cautiously optimistic about the effect.

"The results of these processes are mixed but the trend lines are good," he told the U.S.-China Economic and Security Review Commission, mandated by the U.S. Congress to keep a close eye on China.

"In engaging China and expanding our cooperation on areas of mutual interest, we are in effect encouraging China to act as a responsible shareholder," he said.

The concept of China as a responsible global shareholder "is not only our objective, but a framework for a process that involves building an important and mutually beneficial relationship" between the countries, he said.

Christensen cited China's cooperation on Iran, North Korea, Afghanistan, Iraq and global health, although other U.S. officials have frequently said Beijing could do more, especially on North Korea and Iran.

However, he said, there were serious differences over weapons proliferation, trade and economic imbalances.

The United States remains concerned about China's military buildup but is "realistic" about China's need to modernize its military as its economy and influence expand, the official said.

Asked about possible military conflict across the Taiwan Straits, Christensen said Chinese officials "are a bit more confident that stability can be maintained in the near term than perhaps they were" a few years earlier.

He described the U.S. approach as "hedging" the outcome of China's rise rather than trying to contain a rival power, as Washington did with the Soviet Union during the Cold War.

That means the United States is trying to "help channel China's growing influence in a positive direction" while maintaining "strong U.S. regional capabilities in case China does not eventually move down a path consistent with our interests," he said.

He said China's global emergence is a natural consequence of its economic growth and development and need not be seen as a threat to the United States.

The United States welcomes the emergence of a China that is peaceful and prosperous and that actively participates in and contributes to international institutions, Christensen said.

The U.S.-China Economic and Security Review Commission was created in October 2000, to monitor, investigate, and submit to the Congress an annual report on the national security implications of the bilateral trade and economic relationship between the United States and China, and to provide recommendations to the Congress for legislative and administrative action.