WASHINGTON (AP) — Average U.S. rates for fixed mortgages declined this week but stayed close to their highest levels in two years.Mortgage buyer Freddie Mac said Thursday that the average rate on the 30-year loan fell to 4.51 percent. That’s down from 4.58 percent last week, the highest since July 2011.The average on the 15-year fixed mortgage dipped to 3.54 percent from 3.60 percent, also the highest since July 2011.Rates have risen more than a full percentage point since May when Chairman Ben Bernanke first signaled that the Federal Reserve might reduce its bond purchases later this year. The purchases have helped keep long-term interest rates low.Mortgage rates remain low by historical standards.