WASHINGTON (AP) — Fixed mortgage rates fell once again to a record low, offering a great opportunity for those who can afford to buy or refinance homes. But few are able to take advantage of the rates.

Freddie Mac says the average rate on the 30-year fixed mortgage fell to 3.89 percent. That's below the previous record of 3.91 percent reached three weeks ago.

The average on the 15-year fixed mortgage ticked down to 3.16 percent. That's down from a record 3.21 percent three weeks ago.

Mortgage rates are lower because they track the yield on the 10-year Treasury note, which fell below 2 percent.

Average fixed mortgage rates hovered around 4 percent at the end of 2011. Yet many Americans either can't take advantage of the rates or have already done so.