NEW YORK, June 19 (Reuters) - U.S. stocks fell sharply on Wednesday, with losses accelerating in afternoon trading after Federal Reserve Chairman Ben Bernanke said the central bank could begin to scale back its stimulus measures later this year.

The Dow Jones industrial average was down 205.66 points, or 1.34 percent, at 15,112.57. The Standard & Poor's 500 Index was down 22.88 points, or 1.39 percent, at 1,628.93. The Nasdaq Composite Index was down 38.98 points, or 1.12 percent, at 3,443.20.