WASHINGTON » The average U.S. rate on the 30-year fixed mortgage inched closer to its record low this week, helping to keep home buying more affordable.

Mortgage buyer Freddie Mac says the rate on the 30-year loan dipped to 3.38 percent. That’s down from 3.40 percent last week. And it’s slightly above the 3.31 percent rate reached in November, the lowest on records dating to 1971.

The average on the 15-year fixed mortgage was unchanged at 2.66 percent. The record low is 2.63 percent.

The rate on the 30-year fixed mortgage averaged 3.66 percent in 2012, the lowest annual average in 65 years, according to Freddie Mac.

Cheaper mortgages are a key reason the housing market began to come back last year. Many economists predict the housing recovery will strengthen in 2013.