A Japanese flotilla arrives at an island also claimed by China. (Antoine Boutheir -- AFP/GettyImages)

As China and Japan continue to wrangle over a chain of uninhabited islands that have sparked protests in both countries, near-miss naval incidents, and lots of tough words, diplomats from both Asian powers are increasingly emphasizing the United States's role in the dispute.

The United States seems to be trying to stay as far away from the dispute as possible. But the fact that both China and Japan already seem to perceive the United States as implicitly involved, simply by virtue of it being the dominant Pacific military and diplomatic power, speaks to the difficulty America may face in navigating the coming Pacific century.

The official U.S. position on the islands -- Diaoyu in Chinese, Senkaku in Japanese, claimed by both -- is a bit contradictory. The State Department says it has no position and leaves it to China and Japan to decide, but also that, in the event of a military conflict over the island, America's treaty with Japan would require it to take that country's side.

Neither Japan nor China seems to see U.S. non-involvement as satisfactory, or even as truly neutral. Tuesday, at a Beijing-organized event, a veteran Chinese diplomat accused the United States of using the islands to stir up Chinese-Japanese tensions. He urged the United States to restrain Japan and push for diplomatic negotiations, which The New York Times called "the most detailed public exposition of China’s views" yet.

Meanwhile, Japan's new ambassador to the United States insisted Wednesday that America's "stance cannot be neutral if it is to respond firmly in the event of use of force or provocation." Chinese ships have been pushing near the islands more aggressively, so Japan may be seeking louder American support as a deterrent.

There are two revealing ironies to this. The first is that the island dispute is at its root about nationalism, about Japan and China treating their respective claims as matters of national pride, to both affirm and be affirmed by their national greatness. But appealing to the superpower on the other end of the Pacific would not seem to convey much in the way of national greatness.

The other irony gets to the Obama administration's effort to open a "Pacific century" of American leadership in Asia. The United States, in this thinking, has been mired for decades in the toxic politics of the Middle East. But the forces driving East Asian regional politics aren't always as clean, manageable, and U.S.-friendly as economic development and trade. Asian nationalisms are some of the strongest in the world, particularly in China and Japan, and the logic of nationalism doesn't always line up with the logic of regional cooperation.

If the United States wants to maintain the sort of leadership position in the Pacific that both China and Japan seem to believe it currently holds, then Asia's powers may continue looking to it on regional disputes such as this one. Indeed, if Japan and China perceive the United States as implicitly involved already, then non-involvement isn't really even an option. Reacting to a dispute like this one wouldn't just mean helping Japan and China through diplomatic negotiations, but wading into the complex, superheated nationalisms of Asia, which are rooted in ancient cultural attitudes, in still-fresh grievances, and in the tricky internal politics of both nations. And you thought the Middle East was complicated.