Federal Reserve Chairman Ben S. Bernanke took his defense of the U.S. central bank's monetary stimulus abroad, saying it will aid the world economy, and implicitly criticized China for keeping its currency weak.

The best way to underpin the dollar and support the global recovery "is through policies that lead to a resumption of robust growth in a context of price stability in the United States," Bernanke said in a speech in Frankfurt today. Countries that undervalue their currencies may eventually inhibit growth around the world and risk financial instability at home, he said.