WASHINGTON — Rates on 30-year mortgages plunged to a record low Thursday after the Federal Reserve launched a new effort to prop up the flailing housing market.

The national average rate on 30-year, fixed mortgages was 4.94 percent on Thursday, according to financial publisher HSH Associates, down nearly a quarter point from a day earlier. That's the lowest on HSH's records, which date back to 1979.

For borrowers with stable jobs and good credit, it represents an opportunity to refinance at the lowest rates in decades.

Plus, some mortgage brokers were disappointed on Thursday, saying lenders had not pushed down rates as dramatically as they had hoped. Lenders that are not connected to banks and must rely on short-term funding are having trouble raising cash.

"The problem is: We're still not seeing the injection of capital from the private sector," said Douglas Braden, a broker with Northern Colorado Mortgage Co.