The U.S. Treasury agreed yesterday to pump $3.8 billion - a third round of bailout money - into GMAC Financial Services to shore up the money-bleeding operations of the company's residential-mortgage arm, which employs 1,800 people in Fort Washington.

GMAC said the infusion, which gives the government a majority ownership of the home and auto lender, positions it to "explore strategic alternatives" - possibly including a sale - for the troubled mortgage unit, Residential Capital L.L.C., known as ResCap.

The Treasury Department said the new aid, which comes from a taxpayer-financed bailout fund, was less than the roughly $6 billion the government had earlier thought GMAC would need to stabilize the company.

The fresh infusion from the $700 billion Troubled Asset Relief Program is on top of $12.5 billion in taxpayer money Detroit-based GMAC had already received from the government. The new agreement will boost federal ownership in GMAC to 56 percent from 35 percent.

Even with the increased stake, Treasury officials said the government intended to stick to its policy of leaving day-to-day business decisions about financing to GMAC management. Still, with the additional stake, the government will have the right to appoint two more directors to the company's board, Treasury officials said.

GMAC will continue to be subject to executive-pay restrictions imposed by the government's pay czar.

Shoring up GMAC has been a major component of the Obama administration's massive effort to rescue ailing automakers General Motors Co. and Chrysler Group L.L.C. The lender provides critical wholesale financing to thousands of GM and Chrysler dealers, allowing them to stock their showroom floors with vehicles.

ResCap, which will get $2.7 billion of the new government money, is based in Minneapolis, but major mortgage operations are based in Fort Washington. The local workers also support GMAC's Ally Bank and perform general corporate functions.

ResCap was one of the nation's biggest suppliers of subprime mortgages, or home loans made to people with the weakest credit. GMAC reported losses in eight of the last nine quarters, driven in part by defaults on the home loans.

ResCap, which lost $747 million in the third quarter, will take a new $2 billion write-down on mortgage losses, the company said yesterday.

A separate part of GMAC - for commercial mortgages - was sold in 2006 and is now an independent company, Capmark Financial Group Inc., of Horsham.

GMAC was obligated by the Treasury Department to raise $11.5 billion in additional capital earlier this year after failing the government's stress test for banks, largely because of ResCap's big losses.

However, GMAC had difficulty raising money because of its financial woes, making an extra government infusion necessary.

Even after the latest shot of capital, the government will likely take steps to help GMAC as it tries to ensure the recovery of GM and Chrysler, said Kirk Ludtke, senior vice president at CRT Capital Group L.L.C. That includes helping GMAC refinance its debt as it comes due, he said.

"The government has come this far, it is not going to destabilize GMAC at this point," Ludtke said.

GMAC remains on shaky financial ground. Last month, it reported a quarterly loss of $767 million, though the results were an improvement over a giant loss a year earlier.

The company also has been hurt by the rapid decline of the U.S. auto industry after sales crumbled. Sales of cars and trucks were down 24 percent through November compared with the same period a year earlier. The industry is expected to sell about 10 million cars this year, one of the worst performances for auto sales in decades.

Still, GMAC's auto-lending business has shown some signs of revival. The auto-financing division earned a profit of $395 million during the third quarter.

Ally Bank has also been a bright spot, bringing in billions of dollars in new deposits by offering relatively high interest rates. It now accounts for about 29 percent of GMAC's assets.