Federal Reserve chairman Ben Bernanke has defended measures taken by the bank to bolster the US economy.
Brazil said US monetary easing to keep interest rates low and weaken the dollar has hurt emerging economies.
And International Monetary Fund chief Christine Lagarde warned of consequent asset bubbles developing in emerging nations.
But Mr Bernanke said in Tokyo on Sunday that measures taken by the Fed and other central banks boosted global growth.
The Fed has maintained a low interest rate policy for several years, pumping about $US2.3 trillion into the US economy to bolster growth.
There have also been huge stimulus measures in Europe and Japan.
Critics say such moves, especially by the United States, drive down the value of the dollar and spark capital flows into emerging nations.
The Fed next meets on 23-24 October. No announcements of any major moves are expected.