Here, we have to get past a common misunderstanding: the view that the Chinese have us over a barrel, because we don’t dare provoke China into dumping its dollar assets.

What you have to ask is, What would happen if China tried to sell a large share of its U.S. assets? Would interest rates soar? Short-term U.S. interest rates wouldn’t change: they’re being kept near zero by the Fed, which won’t raise rates until the unemployment rate comes down. Long-term rates might rise slightly, but they’re mainly determined by market expectations of future short-term rates. Also, the Fed could offset any interest-rate impact of a Chinese pullback by expanding its own purchases of long-term bonds.

It’s true that if China dumped its U.S. assets the value of the dollar would fall against other major currencies, such as the euro. But that would be a good thing for the United States, since it would make our goods more competitive and reduce our trade deficit. On the other hand, it would be a bad thing for China, which would suffer large losses on its dollar holdings. In short, right now America has China over a barrel, not the other way around.

So we have no reason to fear China. But what should we do?

Some still argue that we must reason gently with China, not confront it. But we’ve been reasoning with China for years, as its surplus ballooned, and gotten nowhere: on Sunday Wen Jiabao, the Chinese prime minister, declared — absurdly — that his nation’s currency is not undervalued. (The Peterson Institute for International Economics estimates that the renminbi is undervalued by between 20 and 40 percent.) And Mr. Wen accused other nations of doing what China actually does, seeking to weaken their currencies “just for the purposes of increasing their own exports.”

But if sweet reason won’t work, what’s the alternative? In 1971 the United States dealt with a similar but much less severe problem of foreign undervaluation by imposing a temporary 10 percent surcharge on imports, which was removed a few months later after Germany, Japan and other nations raised the dollar value of their currencies. At this point, it’s hard to see China changing its policies unless faced with the threat of similar action — except that this time the surcharge would have to be much larger, say 25 percent.

I don’t propose this turn to policy hardball lightly. But Chinese currency policy is adding materially to the world’s economic problems at a time when those problems are already very severe. It’s time to take a stand.

Critics of China say it is keeping the yuan undervalued to gain an advantage in the international marketplace. A cheaper yuan makes Chinese goods less expensive in the United States and American goods more expensive in China. As a result, American producers find it harder to compete with Chinese imports in the United States and to sell their own exports in China.

There is, however, another side to the story. The loss to American producers comes with a gain to the many millions of American consumers who prefer to pay less for the goods they buy.

The situation is much the same as when the price of imported oil falls, as it has done in recent months. Domestic oil producers may see lower profits, but American consumers are better off every time they fill up their tanks. Consumers similarly gain when a cheap yuan reduces the prices of T-shirts and televisions imported from China.

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Perhaps the oddest thing about Mr. Geithner’s move is that his complaint seems out of date. The yuan-dollar exchange rate has moved considerably in recent years. After a long period of completely fixing the exchange rate, China allowed its currency to start moving in July 2005. Since then, it has appreciated by 21 percent.

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DIRECTING attention to the China currency issue amid a worldwide recession and growing fears of depression is more than a distraction. It is downright counterproductive. Senators Charles E. Schumer, Democrat of New York, and Lindsey Graham, Republican of South Carolina, have long proposed dealing with the yuan undervaluation by imposing tariffs on Chinese imports. The Treasury secretary’s comments risk stoking those protectionist embers.

Indeed, protectionist influences seem to be finding their way into the stimulus bill winding its way through Congress. The bill passed by the House included a provision banning the use of foreign iron and steel in infrastructure projects. The Senate has adopted a somewhat more flexible restriction (after voting down an amendment by John McCain to strip the “Buy American” provision from the bill).