Recently, I met a retired British diplomat who claimed with some pride that he was the man who had invented the phrase, “the management of decline”, to describe the central task of British foreign policy after 1945. “I got criticised”, he said, “but I think it was an accurate description of our task and I think we did it pretty well.”

No modern American diplomat – let alone politician – could ever risk making a similar statement. That is a shame. If America were able openly to acknowledge that its global power is in decline, it would be much easier to have a rational debate about what to do about it. Denial is not a strategy.

President Barack Obama has said that his goal is to ensure that America remains number one. Even so, he has been excoriated by his opponents for “declinism”. Charles Krauthammer, a conservative columnist, has accused the president of embracing American weakness: “Decline is not a condition,” he declared. “Decline is a choice.” The stern rejection of “declinism” is not confined to the rabid right. Joseph Nye, a Harvard professor and doyen of US foreign policy analysts, regards talk of American decline as an intellectual fad – comparable to earlier paranoia about the US being overtaken by Japan. Thomas Friedman, a New York Times columnist, has just published a book that is subtitled “What went wrong with America – and how it can come back”.