Finally, renminbi revaluation would reduce the risk of potentially serious international friction over trade. The problem is that as the dollar weakens against other world currencies  notably the euro and the Japanese yen  so does the renminbi, magnifying China’s already large advantage in global export markets. The burden of post-crisis adjustment falls disproportionately outside Chimerica. Unless China’s currency is revalued, we can expect an uncoordinated wave of defensive moves by countries on the wrong side of Chimerica’s double depreciation. Already we are seeing the danger signs. Last month Brazil imposed a tax on “hot money”  large, volatile flows of foreign investment that may exit an economy as quickly as they appeared  to try to slow the appreciation of its currency, the real. A number of Asian economies last week intervened to weaken their own currencies relative to the dollar. Similar currency games were a feature of the worst economic decade of the 20th century, the 1930s.

Historically, as production costs and income levels in countries have risen, their currencies have adjusted against the dollar accordingly. From 1960 to 1978, for example, the deutsche mark appreciated cumulatively by almost 60 percent against the dollar, while the Japanese yen appreciated by almost 50 percent. The lesson is that exporters can live with substantial exchange rate revaluations so long as they are achieving major gains in productivity, as China still is.

To be sure, China’s central bank has suggested that it might be willing to switch from the dollar peg to some form of exchange-rate management, taking account of “international capital flows and movements in major currencies.” But, like the recent Chinese comments about replacing the dollar as the premier international reserve currency, this may be no more than rhetoric.

During his visit to China this week, President Obama must resist the temptation to respond to these overtures with rhetoric of his own. This is not the time for big speeches, but for subtle diplomacy. Right now, Chimerica clearly serves China better than America. Call it the 10:10 deal: the Chinese get 10 percent growth; America gets 10 percent unemployment. The deal is even worse for the rest of the world  and that includes some of America’s biggest export markets and most loyal allies. The question is: What can the United States offer to make the Chinese abandon the dollar peg that has served them so well?

The authorities in Beijing must be made to see that any book losses on its reserve assets resulting from changes in the exchange rate will be a modest price to pay for the advantages they reaped from the Chimerica model: the transformation from third-world poverty to superpower status in less than 15 years. In any case, these losses would be more than compensated for by the increase in the dollar value of China’s huge stock of renminbi assets.

It is also in China’s interest to kick its currency-intervention habit. A heavily undervalued renminbi is the key financial distortion in the world economy today. If it persists for much longer, China risks losing the very foundation of its economic success: an open global trading regime.

And this is exactly what President Obama can offer in return for a substantial currency revaluation of, say, 20 percent to 30 percent over the next 12 months: a clear commitment to globalization and free trade, and an end to the nascent Chinese-American tariff war.

For as long as the People’s Republic has existed, the United States has been the principal upholder of a world economic order based on the free movement of goods and, more recently, capital. It has also picked up the tab for policing the oil-rich but unstable Middle East. No country has benefited more from these arrangements than China, and it should now pay for them through a stronger Chinese currency. Chimerica was always a chimera  an economic monster. Revaluing the renminbi will give this monster the peaceful death it deserves.