WASHINGTON » Average U.S. rates on fixed mortgages fell closer this week to their historic lows, making homeownership more affordable and refinancing more attractive.

Mortgage buyer Freddie Mac says the average rate for the 30-year fixed loan dipped to 3.41 percent from 3.43 percent last week. That’s not far from the 3.31 percent rate reached in November, which was the lowest on records dating back to 1971.

The average rate on the 15-year fixed mortgage slipped to 2.64 percent from 2.65 percent the previous 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. Sales of new and previously occupied homes are up this year, prices are rising and builders broke ground on homes in March at the fastest annual pace in nearly five years.

Mortgage rates are low because they tend to track the yield on the 10-year Treasury note, which has fallen in recent weeks.

The Federal Reserve has been buying Treasury bonds since the fall. That has helped to lower the yield. And in recent days, concerns that the U.S. and global economies are slowing have led investors to shift money into safer assets, like Treasurys, and away from stocks. Greater demand for Treasurys raises their price and lowers their yield.

The yield fell to 1.69 percent in midday trading today, near its lowest level of the year.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country on Monday through Wednesday each week. The average doesn’t include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for 30-year mortgages fell 0.1 to 0.7 point. The fee for 15-year loans held steady at 0.7 point.

The average rate on a one-year adjustable-rate mortgage ticked up to 2.63 percent from 2.62 percent last week. The fee for one-year adjustable-rate loans rose to 0.4 point, up from 0.3.

The average rate on a five-year adjustable-rate mortgage fell to 2.60 percent from 2.62 percent. The fee held at 0.5 point.