Wall Street opens flat on Fed uncertainty

NEW YORK (Reuters) - U.S. stocks opened flat on Friday as investors continued to question how soon central banks would rein in their stimulus programs.

The Dow Jones industrial average was down 16.82 points, or 0.11 percent, at 15,159.26. The Standard & Poor's 500 Index was down 1.58 points, or 0.10 percent, at 1,634.78. The Nasdaq Composite Index was down 2.29 points, or 0.07 percent, at 3,443.08.

(Reporting by Ryan Vlastelica; Editing by James Dalgleish)