Mortgage rates in the U.S. fell to the lowest level in Freddie Mac records after the Federal Reserve announced a plan to reduce borrowing costs even further.

The average rate for a 30-year fixed loan dropped to 4.01 percent in the week ended today from 4.09 percent, Freddie Mac said in a statement. That's the lowest in the McLean, Virginia- based company's records dating back to 1971. The average 15-year rate declined to 3.28 percent from 3.29 percent last week.

Yields on 10-year Treasuries, a guide for consumer loans, touched the lowest level in more than a half-century, after the central bank said on Sept. 21 that it would begin a program aimed at boosting the economy and lowering mortgage rates. The effort, called Operation Twist, would replace shorter-term securities in the Fed's portfolio with longer-term debt. Policy makers also plan to support the home-loan market by reinvesting maturing housing debt into mortgage-backed securities.

"Mortgage rates have fallen some ways already, but they probably haven't fully caught up with the decline in the 10-year Treasury," Paul Dales, senior U.S. economist at Capital Economics Ltd. in Toronto, said in a telephone interview yesterday. "It's possible the effects of Operation Twist will drag 10-year yields down further, thereby weighing on mortgage rates more."