Federal Reserve Chairman Ben S. Bernanke spoke dire words during a hearing before the Senate Banking Committee on Tuesday. Bernanke told senators that “economic activity appears to have decelerated somewhat” and that “the reduction in the unemployment rate seems likely to be frustratingly slow.” He did not say whether the Federal Reserve plans to do more to boost growth. He also warned lawmakers that federal spending cuts and tax hikes that automatically take effect in 2013 if Congress does not act to extend the Bush-era tax cuts, is the biggest threat to the nation’s economy. He urged lawmakers to “Do no harm.”