WASHINGTON — Average U.S. rates on 30-year and 15-year fixed mortgages dropped to record lows again this week, with the 15-year loan dipping below 3 percent for the first time ever. Low rates have helped brighten the outlook for home sales this year.

Mortgage buyer Freddie Mac says the average rate on the 30-year loan fell to 3.75 percent. That’s down from 3.78 percent last week and the lowest since long-term mortgages began in the 1950s.

The 15-year mortgage, a popular refinancing option, slipped to 2.97 percent. That’s down from 3.04 percent last week.

Rates on the 30-year loan have been below 4 percent since early December.