good article from Stratfor concerning the increasing number of disputes between Japan and China over ownership of islands in the East China sea. But perhaps the most fascinating part is the shortest. Everyone is fully aware of the dispute between the two nations. However, what many don't realize is that since the 1930s the US has been alternating support for which ever party is considered weaker. From the 1930s to the end of World War II that was China. Once the nationalists in China were defeated, and moved to Taiwan, the US spent time and resources strengthening Japan to counter the communist power bloc. Currently, the US is trying to maintain a balance between a rising but internally fracturing China and a slumped but internally cohesive Japan.
While the US doesn't want outright conflict between the two nations; it does want to make sure no one power can become strong enough to become a regional hegemon. The US is the top dog in the pacific and it intends to remain so. Ultimately US interests and positioning determines the actions of our government. With the economic and social situation starting to deteriorate in China the US may slowly become more conciliatory towards China; eventually. There is a chance that China may lose control of its state encourage protests and the resulting chaos could result in a more militarily bellicose nation. China doesn't want to risk its trade relationships, but before the health of the nation comes the primacy of the party.
Either way, expect to see Washington becoming more involved in these types of disputes. The US is slowly reengaging the western pacific, which is a reintroduction of our foreign policy focus shift since the end of the cold war that was temporarily halted due to 9/11. Along with the introduction of China's first carrier into active service, though it still does not compare to a US Navy carrier, and the that region of the world will become more tense. Both the US and China are ultimately playing a chess game to determine who will be the hegemon in the pacific. The US has the advantage currently, an advantage I expect them to maintain, however, things could move in unexpected ways.