WASHINGTON (AP) — Average U.S. rates on fixed mortgages fell closer this week to their historic lows, increasing the affordability of buying homes and refinancing.

Mortgage buyer Freddie Mac says the average rate for the 30-year fixed loan slipped to 3.40 percent from 3.41 percent last week. That's near the 3.31 percent rate reached in November, which was the lowest on records dating back to 1971. It was the key rate's fourth straight weekly decline.

The average rate on the 15-year fixed mortgage declined to 2.61 percent from 2.64 percent last week. That nearly matches the record low of 2.63 percent, also reached in November.

Low mortgage rates are helping drive a housing recovery that began last year. Home prices are rising. Sales of new and previously occupied homes are up this year.