Fed owns up to global risks in statement shift

SAN FRANCISCO/WASHINGTON (Reuters) - In the U.S. Federal Reserve's arsenal of tools the characterization of economic risks is heavy artillery, used to flag the moments when major events like the 2003 Iraq war or the near crack-up of the euro zone in 2011 make forecasting even trickier than usual. The U.S. central bank has now put the world on notice that the slide in oil prices and sharp slowdown in global growth may rank as one of those very shocks, capable of changing the Fed's bias from imply