Fed's Yellen says global risks could pose U.S. growth threat

By Howard Schneider and Lindsay Dunsmuir WASHINGTON (Reuters) - Tightening financial conditions driven by falling stock prices, uncertainty over China and a global reassessment of credit risk could throw the U.S. economy off track from an otherwise solid course, Federal Reserve Chair Janet Yellen said on Wednesday in prepared testimony to Congress. In remarks that combined a steady-as-she-goes account of Fed policy with an acknowledgement of intensifying risks, Yellen said there are good reasons