A few months ago Tim Geithner, the US Treasury secretary, assured a group of Chinese students in Beijing that their country's US dollar investments were in good hands. “Chinese assets are very safe,” Mr Geithner said. His comments brought the house down.
White House officials will be hoping that Barack Obama can avoid a similar loss of face on Monday when he meets a group of students in Shanghai for the set piece “town hall” that has become the US president's signature event.
The chances are that he will. But no amount of dexterity can disguise the fact that Mr Obama's visit to China crystallises a big shift in the global centre of gravity over the past few years. Just a decade ago Bill Clinton persuaded Capitol Hill that China's membership of the World Trade Organisation would strengthen the forces of democracy within China.