Shortly before President Barack Obama visited Beijing for the first time, he set out US policy to China: “We welcome China’s efforts to play a greater role on the world stage,” he declared. “Power does not need to be a zero-sum game and nations need not fear the success of each other.”

I am prepared to bet that Mr Obama will say something very similar when he welcomes President Hu Jintao to Washington this week. And I’m sure the Chinese leader will respond with warm words.

But, beneath the rhetoric, things are shifting fast. There is a long and growing list of disputes between China and the US. Old arguments over Taiwan and human rights are now supplemented by a new set of disputes over currency, trade, the South China Sea and China’s military build-up.