SANTA BARBARA, Calif.  Ben S. Bernanke, the chairman of the Federal Reserve, said on Monday that Asian nations were pulling the global economy out of its downturn but warned that both Asia and the United States needed to do more to reduce global trade imbalances.

Speaking at a conference on Asia hosted by the Federal Reserve Bank of San Francisco, Mr. Bernanke said Asian countries had bounced back from the global recession faster than the rest of the world and had reported “impressive” growth.

“Asia appears to be leading the global economic recovery,” the Fed chairman said, noting that the region as a whole expanded at an annual rate of 9 percent during the second quarter and that some countries, including China, grew at rates of more than 10 percent.

But Mr. Bernanke also warned that huge trade imbalances between the United States and the rest of the world had played a central role in the global economic crisis and that they could do so again.