For a while, the world became infatuated with the notion of a Group of Two. The idea was that a weary America and a resurgent China would co-operate ever more closely to take on the most intractable global problems. Only through accelerating Beijing's metamorphosis into a “responsible stakeholder” – in Robert Zoellick's slightly condescending phrase – would we stand a chance of tackling issues such as global warming and financial imbalances.

Naturally, the idea had its critics. Europe, Japan and India, for starters, were understandably derisive of the suggestion that the US and China could somehow club together to set the world to rights. There were also early stumbling blocks, most notably the failure of last year's Copenhagen climate change summit, which many blamed on China, and Beijing's reluctance to impose sanctions on nuclear rebels Iran and North Korea.

Nevertheless, Washington has made an attempt to advance what looks like a G2 agenda. At the very least it has sought to flatter China to lure it further into the international arena. When Barack Obama, US president, visited China in November, he put enormous store in securing the signature of a joint document in which the two declared a “new era” in their relations. They promised to “nurture, and deepen bilateral strategic trust” and said they shared “increasingly important common responsibilities on many major issues concerning global stability and prosperity.”