Fannie Mae, which was placed into conservatorship and received a $100 billion commitment from the Treasury Department, announced on Monday that it lost $29 billion in the third quarter. It said the number of loans in its portfolio that were in foreclosure or delinquent by more than three months had jumped to 1.72 percent in September. Fannie Mae said it had reduced the value of its assets by $21.4 billion for the third quarter and increased credit loss reserves by 75 percent, to $15.6 billion. In addition, it disclosed that if “current trends in the housing and financial markets continue or worsen,” it may have “negative net worth” by December 31, 2008, requiring it to draw on Treasury’s commitment to avoid mandatory receivership.

In its Form 10-Q filing with the Securities and Exchange Commission on Monday, the giant mortgage company hinted that even Treasury’s $100 billion commitment may not be sufficient: “If we continue to experience substantial losses in future periods or to the extent that we experience a liquidity crisis that prevents us from accessing the unsecured debt markets, this commitment may not be sufficient to keep us in solvent condition or from being placed into receivership.”

The mortgage company acknowledged that it had a limited ability to issue debt maturing past one year, citing market conditions, the lack of an explicit federal guarantee and competition from bank borrowings that are guaranteed by the FDIC under its Temporary Liquidity Guarantee Program.

Fannie Mae must have ready access to the credit markets to finance purchases for its $761 billion mortgage portfolio and pay off debt as it matures. The mortgage company has more than $138.6 billion in short-term debt maturing over the next two months.

Fannie Mae and Freddie Mac were both seized by regulators in early September setting off a firestorm of government intervention in the credit and capital markets.