By Kate Gibson
NEW YORK (MarketWatch) -- The U.S. stock market gained strength Wednesday, with the S&P 500 index SPX +0.66% at its session high, after the Federal Reserve bolstered stimulus to the economy. The central bank said it would add $45 billion in Treasury note purchases to its $40 billion a month purchases of mortgage-backed bonds. The Fed also said it would keep official rates near zero so long as the unemployment rate remains above 6.5% and inflation is not forecast to rise above 2.5%. The Dow Jones Industrial Average DJIA +0.48% rose 59.92 points, or 0.5%, to 13,308.36. The S&P 500 advanced 9.16 points, or 0.6%, to 1,437. The Nasdaq Composite COMP +0.35% climbed 9.77 points, or 0.3%, to 3,032.07.
