But it remains to be seen whether the move will significantly rebalance the global trade picture. The People’s Bank of China was cautious in its statement about how far its currency, the renminbi, might fluctuate, warning explicitly that “the basis for large-scale appreciation of the RMB exchange rate does not exist.” Chinese officials said the renminbi would move in relation to an unspecified basket of currencies, not just the dollar. Experts said that depending on how the system was designed, China could avoid rapid fluctuations.

Mr. Geithner alluded to this in a statement, saying, “This is an important step, but the test will be how far and how fast they let the currency appreciate.”

The first sign of how much currency appreciation will be tolerated is likely to come Monday morning, when the Chinese government will set the initial trading band for the value of the renminbi in Shanghai trading.

China has kept its currency value low since mid-2008 by pegging it to that of the dollar and not letting it fluctuate. Any trend in the renminbi’s value would have been higher without the peg, making China’s goods more expensive to foreign consumers and possibly slowing the country’s export-based economy.

In its statement Saturday, the central bank said that the Chinese economy was strengthening after the crisis and that it was “desirable to proceed further with reform” of the currency. Tellingly, the announcement was made almost simultaneously in Chinese and in English, a rare occurrence, and Chinese officials advised foreign governments beforehand that they were about to take a new stance on currency policy, according to an American official.