Average US rate on 30-year mortgage inches up to 3.91 percent; 15-year loan up to 3.11 percent

For the second straight week, average long-term U.S. mortgage rates inched up this week as financial markets awaited the Federal Reserve's crucial decision on interest rates.

Mortgage giant Freddie Mac says the average rate on a 30-year fixed-rate mortgage edged up to 3.91 percent from 3.90 percent a week earlier. The rate on 15-year fixed-rate mortgages rose to 3.11 percent from 3.10 percent.

Capping months of feverish speculation, Fed policymakers may finally raise a key interest rate on Thursday. A rate hike by the Fed could bring higher rates for home loans. The Fed has kept its key short-term rate at a record low near zero since the financial crisis struck seven years ago.