A senior U.S. official issued a subtle but clear message to the Japanese government suggesting Tokyo tone down its rhetoric and actions in its intensifying territorial spat with Beijing.

"We have conveyed privately our desire for quiet diplomacy and effective diplomacy to take place between all the parties involved," Kurt Campbell, the Obama administration's top diplomat for East Asia, told reporters after visiting Japanese officials in Tokyo. "We made very clear our desire to see cooler heads prevail and the maintenance of peace and stability overall."

Mr. Campbell, an assistant secretary of state, didn't explicitly blame Japan for its behavior in the dispute, nor did he criticize China. Despite questions from reporters suggesting responsibility for one side or the other, Mr. Campbell maintained a neutral tone in describing the situation.

Asked what steps he'd like Japan to take, he said: "We are concerned by some of the actions around the maritime issues. We have conveyed privately our desire for quiet diplomacy, effective diplomacy, to take place between all the parties involved."