WASHINGTON – US government-controlled mortgage finance giant Freddie Mac said late Friday that it would ask the Treasury for an additional 30 to 35 billion dollars to prevent its collapse.

Freddie Mac, which along with its sister institution Fannie Mae was taken over by the government in a September rescue, said that it determined the size of the shortfall while preparing fourth-quarter and full-year 2008 results.

"The amount of the estimated additional draw ... reflects management's current estimate of the impact of operating losses as well as other items that have a direct impact on the company's net worth in the fourth quarter," Freddie Mac said in a filing with the US Securities and Exchange Commission.

The funds would come from a 100-billion-dollar line of credit with the Treasury set up to keep the company at least with positive net worth.

The company noted the amount of the injection needed was only an estimate.

"The actual amount of the draw may differ materially from this estimate as Freddie Mac goes through its internal and external process for preparing and finalizing its financial statements," said the company, formally known as the Federal Home Loan Mortgage Corporation.

Freddie Mac did not reveal the amount of its losses but they appeared huge, given the scale of the recapitalization sought.

The company has already received 13.8 billion dollars from the Treasury after reporting a third-quarter loss of 25.3 billion dollars amid the global financial crisis and housing slump.

It had lost 28.9 billion dollars in the second quarter.

Freddie and Fannie, both government-chartered but shareholder-owned companies designed to provide liquidity to the housing market, were placed under government control in early September in an effort to avert a meltdown in the financial system and offer a backstop for trillions of dollars in outstanding mortgage debt.

Under the plan, the two firms received government-appointed chief executives and shed their shareholder profit mission. The Treasury agreed to inject 100 billion dollars in each company if needed.

In electronic trading after the New York market close, shares in Freddie, which are still traded despite the firm's partial nationalization, dropped 2.94 percent to 66 cents.