The Bush administration last month unveiled a plan to provide unlimited government loans to the two mortgage giants and to purchase stock in the two companies if needed for a period covering the next 18 months.

Many observers say Treasury Secretary Henry Paulson is not interested in protecting common shareholders, only in Fannie and Freddie's ability to support the battered mortgage market.

That means a government rescue might not occur until there is evidence the mortgage companies' are unable to sell short-term debt — an indication they would no longer be able to operate normally.

Shares of the two companies — which together hold or guarantee half the U.S. mortgage debt — have lost more than half their value this week on fears that a government bailout would wipe out common stockholders.

Fannie Mae shares rose 35 cents, or 8 percent, to $4.75 in afternoon trading, while Freddie Mac fell 13 cents, or 4 percent, to $3.12.

Freddie in particular has investors and analysts fearful. The company earlier this year promised to raise $5.5 billion to shore up its finances but has not yet done so and its sinking share price makes raising that money far less feasible.

Fannie Mae's chief executive has sought to reassure investors that no bailout is imminent, and that the company's financial position remains solid.

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AP Business Writer Ieva M. Augstums in Charlotte, N.C. contributed to this report.