TOKYO — At a gathering of business executives in Cambodia this week, Secretary of State Hillary Rodham Clinton plans to urge the expansion of American trade and investment across Asia, particularly in Southeast Asian nations on the periphery of China.

It has become more common these days for the nation’s chief diplomat to play a role as a business booster. But the extra attention devoted to economics is intended to send a message that Washington recognizes that it initially overemphasized the military component of its new focus on Asia, setting up more of a confrontation with China than some countries felt comfortable with.

“There’s a nervousness that the two of them shouldn’t get into a fight,” said a senior Southeast Asian diplomat, who spoke on the condition of anonymity according to protocol. “No one wants to choose sides” between China and the United States, he said.

Indeed, both sides have an interest in channeling their rivalry into trade more than weaponry, even as it is clear that China sees itself as increasingly having the upper hand in the region.