Because the government can hold those mortgages as long as it wants, officials are betting the government will be repaid and that taxpayers may even earn a profit if the market value of the loans climbs in the years to come.

To entice private investors like hedge funds and private equity firms to take part, the F.D.I.C. will provide nonrecourse loans  that is, loans that are secured only by the value of the mortgage assets being bought  worth up to 85 percent of the value of a portfolio of troubled assets.

The remaining 15 percent will come from the government and the private investors. The Treasury would put up as much as 80 percent of that, while private investors would put up as little as 20 percent of the money, according to industry officials. Private investors, then, would be contributing as little as 3 percent of the equity, and the government as much as 97 percent.

The government would receive interest payments on the money it lent to a partnership and it would share profits and losses on the equity portion of the investment with the private investors.

Image The F.D.I.C.  headed by Sheila C. Bair  will provide loans to entice private investors to participate in the program. Credit... Joshua Lott/Bloomberg News

Ever since last fall, industry analysts and policy makers in Washington have argued that the banking system’s biggest problem was the huge pile of troubled mortgages and other loans on bank balance sheets.

Risk-taking institutional investors, like hedge funds and private equity funds, have refused to pay more than about 30 cents on the dollar for many bundles of mortgages, even if most of the borrowers are still current. But banks holding those mortgages, not wanting to book huge losses on their holdings, have often refused to sell for less than 60 cents on the dollar.