PHILADELPHIA (Reuters) - The Federal Reserve is actively preparing for the possibility that the United States could default as a deadline for raising the government's $14.3 trillion borrowing limit looms, a top Fed policymaker said on Wednesday. (http://feeds.feedburner.com/~ff/reuters/topNews?d=yIl2AUoC8zA) (http://feeds.feedburner.com/~ff/reuters/topNews?i=uLvOUWV20JU:Cd4cPwA_lcI:V_sGLiPBpWU) (http://feeds.feedburner.com/~ff/reuters/topNews?i=uLvOUWV20JU:Cd4cPwA_lcI:-BTjWOF_DHI) (http://feeds.feedburner.com/~r/reuters/topNews/~4/uLvOUWV20JU)