For almost a decade, all the talk among key United States officials and strategy experts was about the rise of China and what the US could do to prevent, constrain or accommodate itself to a development that seemed so inevitable as to be effectively preordained.

But over the past month or so, the debate in official Washington has swung 180 degrees in the opposite direction. The fashionable talk now is about what the US should do to handle a China that may have already peaked in its economic power and could soon decline.