Raising interest rates too late is safer than acting too early, an influential Federal Reserve official said on Friday, endorsing a high-profile research paper that argues the U.S. economy, given time, can rebound to the strong growth rate to which Americans are accustomed. The paper by four top U.S. economists, presented on Friday to a roomful of powerful central bankers in New York, argues the Fed would be wise to keep rates at rock bottom for longer than planned and then tighten monetary policy more aggressively.