"Previously, we said house prices would fall at least 15 percent nationally, peak to trough. Today's challenging economic environment suggests that the housing market is far from stabilizing," Richard Syron, the chairman and CEO of Freddie Mac, told investors in a conference call held to discuss the company's earnings.

"As a result, we now believe that national home prices will fall 18 to 20 percent peak to trough. ... The long and short of it is that we now think that we are half-way through the overall peak-to-trough decline."

Freddie Mac Wednesday posted its fourth straight quarterly loss as it braced for a prolonged housing crisis by setting aside twice as much money for bad loans and setting plans to slash its dividend by at least 80 percent.

The worse-than-expected results come just three weeks after U.S. authorities orchestrated a sweeping effort to prop up the second-biggest provider of U.S. residential mortgage funding and its rival Fannie Mae , Freddie Mac affirmed a commitment to raise fresh capital.

Freddie Mac's chief financial officer repeated that it continues to maintain a surplus over regulatory capital requirements, and said the company can wait for "choppy" market conditions to improve before raising capital, which could exceed $5.5 billion.

For the second quarter, McLean, Virginia-based Freddie Mac reported a loss of $821 million, or $1.63 cents per share, compared with a profit of $729 million, or 96 cents per share, a year earlier.

That included the first loss from its holdings of subprime and other risky loans, which formed a significant part of its $2.8 billion in realized and anticipated losses stemming from the steepest U.S. housing downturn since the Great Depression.