The chief of the Federal Reserve refrained from laying out further steps to boost the fragile U.S. economy, but it is likely to have a limited impact on South Korea's financial markets, officials said Saturday. Fed Chairman Ben Bernanke on Friday stopped short of hinting at the third round of quantitative easing, known as QE3 in markets, to support the weakening economy at a conference in Jackson Hole, Wyoming. But the chairman said the central bank still has policy tools to stimulate the economy and will extend its September policy meeting to two days to mull its options.