Sept 25 (Reuters) - U.S. stocks were little changed on Wednesday, with the S&P 500 facing a possible fifth straight day of declines, as the lack of progress in Washington threatened a government shutdown in just six days. The Dow Jones industrial average fell 14.83 points or 0.1 percent, to 15,319.76, the S&P 500 gained 0.73 points or 0.04 percent, to 1,698.15 and the Nasdaq Composite added 8.057 points or 0.21 percent, to 3,776.311.