WASHINGTON (AP) — Average U.S. long-term mortgage rates ticked down for the third straight week, a positive trend for potential homebuyers.

Mortgage company Freddie Mac says the nationwide average for a 30-year mortgage declined to 3.97 percent this week from 3.99 percent last week. Rates are now about a half-point lower than at the beginning of the year.

Long-term mortgage rates fell as low as 3.31 percent toward the end of 2012, partly because of the Federal Reserve's bond-purchase program, which was intended to keep rates low. That program has since ended.

Rates have fallen in recent weeks amid economic slowdowns in Europe and China and the start of a recession in Japan.

The average for a 15-year mortgage, a popular choice for people who are refinancing, was unchanged at 3.17 percent.