The Dow Jones industrial average closed with a loss of three points at 13,245 Wednesday, while the Standard & Poor's 500 index edged up less than a point to 1,428. The Nasdaq composite fell eight points to end the day at 3,014.
Stocks moved higher in the early afternoon after the Fed announced the latest extension of its bond-purchasing program and low-interest rate policy. The Dow gained as much as 81 points before slumping in the late afternoon.
Traders were also watching budget talks in Washington.
Falling stocks narrowly outnumbered falling ones on the New York Stock Exchange. Volume was in line with the recent average at 3.6 billion shares.