Chinese officials are fighting back. In a rare interview published last weekend by Caixin, a Chinese magazine, Zhou Xiaochuan, the governor of China’s central bank, said, “China has the largest volume of foreign exchange reserves in the world, and we will not let speculative forces dominate market sentiment.”

China’s reserve hoard is a byproduct of the way it manages its currency.

During China’s biggest boom years, its currency could have risen in value as huge sums in dollars, euros and yen flowed into the country. Instead, Beijing tightly controlled the value of the renminbi, buying up much of the inflows and putting them into its reserves instead. That brought angry accusations from the United States and Europe that it was manipulating its currency to help keep Chinese exports inexpensive and competitive in foreign countries.

Now that the renminbi faces pressure to fall, China is spending its reserves in an effort to prop up the currency. But many American lawmakers and presidential candidates still accuse China of keeping its currency artificially weak.

The reserves are still considerable, more than double Japan’s, which has the world’s second-largest amount. The central bank chief, Mr. Zhou, and others have questioned whether the reserves are too big and the money could be better invested if left in the private sector. Mr. Zhou led a move over the last two years to make it easier for Chinese companies and families to invest their own money overseas, only to find in recent months that the outflows have been disconcertingly fast at times.

China has taken steps to stem further flows out of the country. This winter the Chinese authorities arrested the leaders of underground banks that were converting billions of renminbi into dollars and euros. They also made it harder for Chinese citizens to use their renminbi to buy insurance policies in dollars.