WASHINGTON (AP) — Average long-term U.S. mortgage rates edged lower this week for a third straight week.

Mortgage buyer Freddie Mac says the average rate on a 30-year fixed-rate mortgage slipped to 3.93 percent from 3.95 percent a week earlier. The average rate on 15-year fixed-rate mortgages eased to 3.16 percent from 3.18 percent.

The key 30-year rate was above its level of a year ago, 3.89 percent. Despite the recent declines, the rate has increased significantly overall since the end of October, when it stood at 3.76 percent.

The Federal Reserve is widely expected to raise its key short-term interest rate at its policymaking meeting on Dec. 16. It would be the Fed's first interest-rate hike in nearly a decade.