At the same time, American officials said the United States was also looking at the meeting of top envoys of the three countries in Sydney, Australia, as a means to draw Japan into improving relations with neighboring countries still suspicious of its intentions 60 years after World War II.

Heading toward the end of what aides said would be one of the longest trips by a secretary of state, Ms. Rice joined with the foreign ministers Alexander Downer of Australia and Taro Aso of Japan in welcoming China's "constructive engagement" in East Asia. Australian and American officials acknowledge, however, that the phrase understates the Chinese sphere of influence.

"The tenor of the discussion was how to make China a positive force in the region," said Sean McCormack, the State Department spokesman, briefing reporters on the secretary's plane to American Samoa for refueling. He said the discussion was an effort to add to the web of American alliances in the area, to enhance stability and not threaten China.

Nevertheless, in Indonesia earlier in the week and then in Australia, where Ms. Rice spent nearly three days, she was repeatedly asked by the local news media about American intentions toward China, which has signed an array of economic deals with countries on its rim.

At a news conference in Sydney on Thursday, Ms. Rice reinforced those concerns, criticizing China's military buildup, economic policies and human rights record. Asked if China would see Ms. Rice's trip as a cause for concern, another senior official, speaking anonymously under briefing ground rules, said, "I think we certainly hope so."

Ms. Rice's visit to Australia, from Wednesday night to Saturday afternoon, was long compared with other stops. But American officials said Australia, an ally that has sent forces to Iraq and Afghanistan, had been feeling neglected, and Australian leaders appealed for Ms. Rice to do some public diplomacy to prop up the sagging American image.