WASHINGTON - The Treasury Department is strongly considering a plan to intervene directly in the mortgage industry to dramatically force down rates and stimulate the moribund housing market, according to sources familiar with the proposal.

Under the initiative, Treasury would offer to buy securities that finance newly issued loans for home purchases, according to the sources. But to sell these securities to the government, mortgage lenders would have to charge interest rates of no more than 4.5 percent.

These securities would be purchased primarily from Fannie Mae and Freddie Mac, the financing giants that buy most mortgages from U.S. lenders, according to sources who spoke on condition of anonymity because the plans have not been finalized.

The cost of the plan and source of funding remain unclear. One possibility is for the Treasury to raise money by issuing bonds to the public at 3 percent interest. This could allow the government to turn a profit because it would be buying securities that pay 4.5 percent.

At a meeting attended by the Treasury's Interim Assistant Secretary for Financial Stability Neel Kashkari and the National Association of Realtors in mid-November, senior Treasury officials said they were optimistic that subsidizing lower mortgage rates with taxpayer dollars would help revive the housing market, sources said.

Treasury officials told the Realtors that the plan could be a more effective way to help homeowners than focusing efforts solely on borrowers who are struggling to meet their monthly payments, the sources said. Democratic lawmakers have been advocating a proposal to modify the mortgages of distressed homeowners.

Treasury spokeswoman Brookly McLaughlin said she would not comment.