By MATT OTT
AP Business Writer
WASHINGTON (AP) — Average long-term U.S. mortgage rates rose this week but remain at historically low levels, just as the Federal Reserve prepares to raise its main borrowing rate. The average rate on a 30-year loan rose to 3.85% this week from 3.76% last week, mortgage buyer Freddie Mac reported Thursday. The average rate on 15-year, fixed-rate mortgages, popular among those refinancing their homes, climbed to 3.09%. Last week, Fed Chair Jerome Powell said he supported a traditional quarter-point increase in the Federal Reserve’s benchmark short-term interest rate when the Fed meets later this month.