ST. LOUIS (Reuters) - The Federal Reserve should raise U.S. interest rates only gradually and patiently, a top Fed official said on Thursday, but it is "very important" to make the effort to normalize rates.

Low rates and excessive accommodation can cause distortions investment and hiring, said Dallas Fed President Robert Kaplan, speaking in St. Louis at Washington University.

(Reporting Ann Saphir; Editing by Sandra Maler)