By RUTH SIMON

The Obama administration on Thursday laid out additions to its housing-rescue plan that are designed in part to make it easier for financially troubled homeowners to sell houses that are worth less than their mortgages.

The newest initiative creates a standardized process and adds incentives for so-called short sales, in which a borrower -- with lender approval -- sells the home for less than the amount owed.

The government also said it would make it simpler for borrowers to voluntarily transfer ownership of properties to mortgage companies through a "deed in lieu" of foreclosure, helping the companies avoid a potentially costly and time-consuming foreclosure process.

Administration officials said the new initiatives could help hundreds of thousands of borrowers or more.

The guidelines come nearly three months after the administration laid out its $75 billion housing-rescue plan, which uses financial incentives to encourage mortgage companies and investors to modify troubled loans. The latest announcement is aimed in part at borrowers who can't be helped by a loan modification.

Efforts to implement the programs are just getting off the ground. Government officials said Thursday that mortgage-servicing companies have offered more than 55,000 trial modifications to financially troubled borrowers and that thousands of those borrowers have begun making loan payments under the program.

In addition, roughly 3,600 borrowers have lowered their loan payments under a program that allows borrowers who have little or no equity to refinance, provided that their loan is owned or backed by government-controlled mortgage giants Fannie Mae and Freddie Mac. Fannie has received more than 51,000 applications for the program.

But not all borrowers can be helped by such efforts, often because they have too much total debt or not enough income or because modifying the loan may not be economical for an investor or lender compared with foreclosure.

The government will pay mortgage-servicing companies up to $1,000 and borrowers up to $1,500 for successful short sales or "deeds in lieu" transactions. It will also spend up to $1,000 to help defray the cost of getting holders of second mortgages to release their liens so these transactions can be completed.

Short sales have accounted for 15% to 20% of sales of existing homes this year, according to the National Association of Realtors. A short sale can result in lower losses to investors compared with a foreclosure but needs lender approval and can take three to four months to complete, said Bill Etchegaray, a real-estate agent with Century 21 Superstars in Yorba Linda, Calif.

The incentive payments to mortgage-servicing companies and streamlined process could help clear the logjam of distressed home loans, said Thomas Lawer, an independent housing economist, adding that "it's crystal clear" that short sales are often preferable to a foreclosure. But "giving borrowers money to encourage them to sell their homes without having to repay their debt is a slap in the face to everyone else," he added.

Another part of the program provides additional payments to lenders, servicers and investors for loan modifications in areas where home prices have been dropping. Payments under this program could in some cases total thousands of dollars per loan, administration officials said, and are designed to offset concerns that investors will face additional losses if the modified loans redefault.

So far, 14 mortgage-servicing companies have signed up to participate in the loan-modification program, and 75% of loans are now covered by the plan. The firms include Bank of America Corp., Citigroup Inc., J.P. Morgan Chase & Co. and Wells Fargo & Co. Other mortgage companies, including SunTrust Corp., PNC Corp. and American Home Mortgage Servicing Inc., said they are still evaluating the program. HSBC Mortgage Corp. said it has been implementing the Obama program for borrowers with Fannie or Freddie mortgages, but is still evaluating the program for loans it owns. PNC is applying the guidelines of the Obama plan to loans owned or guaranteed by Fannie and Freddie, but hasn't yet signed a contract with the government that would require it to apply those same guidelines to loans it owns or services for investors, a company spokesman said.