“Whether China can keep adequate foreign-exchange reserves will depend on what the central bank is up to,” Mr. Zhang said. If the central bank intends to continue to intervene heavily to keep the yuan stable, he said, “the current level of reserves may not be adequate enough

On the other hand, Mr. Zhang said, if the central bank presses ahead on giving the market bigger sway in the exchange rate by reducing intervention and at the same time tightens capital controls, “the reserves will undoubtedly be enough.”

The People’s Bank of China has been doing both, prioritizing the yuan’s stability over market reforms. In recent weeks, while intervening to prop up the currency, the bank has imposed fresh controls aimed at preventing money from leaving the country. That strategy has confused investors both inside and outside China, resulting in both businesses and individuals rushing for the exit.

Western officials including U.S. Treasury Secretary Jacob Lew and the International Monetary Fund’s Christine Lagarde recently have urged Beijing to better communicate its policy intentions with the market.

Senior Chinese officials in recent weeks said they recognize the need for clearer communication to avoid roiling global markets. That said, they ruled out for now the possibility of a one-off sharp devaluation of the yuan as urged by some economists and investors, saying that would undermine Chinese purchasing power just as the government is trying to shift to an economy driven by consumption.