WASHINGTON - The government was moving ahead Wednesday on a fresh multibillion dollar cash infusion to stabilize auto financing company GMAC Financial Services, according to a person with knowledge of the matter.

GMAC, based in Detroit, is instrumental to the operations of automakers General Motors Co. and Chrysler Group L.L.C. It has already received $12.5 billion in taxpayer money and is 35 percent owned by the federal government.

GMAC's mortgage division, Residential Capital L.L.C., or ResCap, is based in Fort Washington, Montgomery County.

The person, who spoke on condition of anonymity because discussions weren't complete, says the new infusion would be in the range of $3 billion more. That would fall short of the roughly $6 billion the government had earlier thought GMAC would need to stabilize the company.

An announcement of the injection could come late Wednesday or on Thursday, the person says.

After the government conducted "stress tests" on financial institutions earlier this year, it demanded that GMAC raise an $11.5 billion capital cushion to help it weather further economic decline. GMAC was unable to raise the funds privately.

The anticipated additional government aid for GMAC would come from the $700 billion taxpayer-financed bailout pot the government set up at the height of the financial crisis last year. The money was intended to shore up banks so that they would boost lending to people and businesses and support the sagging economy. However, money also has been used to help GM, Chrysler, insurance companies and others survive the worst financial crisis and recession since the 1930s.

GMAC has been in negotiations with Treasury officials for months over additional taxpayer aid.

Treasury spokesman Andrew Williams declined to offer details, but said: "Treasury is in discussions with GMAC to ensure its capital needs as determined . . . by the stress tests are met."

The Wall Street Journal was the first to report on Tuesday that GMAC would receive an additional $3.5 billion in government aid.

GMAC spokeswoman Gina Proia on Tuesday night declined comment on the newspaper report but said the company "has been conducting a strategic review of its business and evaluating options to address the challenges in its mortgage operation."

Proia said GMAC was trying to position itself to improve its financial performance and repay the U.S. government.

Despite the government aid, GMAC still remains on shaky financial ground. Last month, it reported a quarterly loss of $767 million. The company has struggled under the weight of its ailing mortgage lender, ResCap. The unit was a major dealer in subprime mortgages and is still suffering from soured loans it made during the housing boom. Some analysts have speculated that GMAC might have to shut down ResCap altogether.

However, a bright spot for GMAC has been Ally Bank, its online consumer banking unit. The bank has offered some of the highest interest rates on CDs in the industry, helping bring in billions of dollars in new deposits this year. But the rates have also irked rivals and drawn the attention of regulators, since as the rebranded banking unit of GMAC, Ally has the backing of billions of government dollars loaned to GMAC.

Michael Carpenter, who succeeded Alvaro De Molina as the company's CEO in November, has said the company would need no more than $5.6 billion in aid. Lawmakers estimated the company would receive $2 billion to $5 billion in additional aid.