NEW YORK (CNNMoney.com) -- General Motors cleared a major hurdle in its efforts to sell its GMAC finance unit as the federal agency that insures pensions said the buyer won't be held responsible for the automaker's obligations to retirees.

In a GM (Charts) filing with the Securities and Exchange Commission Thursday, the automaker reported a letter from the Pension Benefit Guaranty Corporation (PBGC) said that it will not as a result of the GMAC sale move to terminate GM's pension plans or impose liability on the buyer of GMAC or its subsidiary.

That clearance was one of the conditions of the sale, according to the filing.

GM agreed in April to sell a 51 percent stake in GMAC to a group led by Cerberus Capital Management, an investment firm.

The unit is by far the largest producer of profits at the troubled automaker, which continues to lose money on its core auto operations. But the sale was made necessary after GM's bonds got cut to junk bond status, which increased the cost of raising capital at GMAC.

Despite some speculation that it might do so, GM says it has no intention to file for bankruptcy protection, which could lead it to terminate its pension plans and dump its obligations on the federal agency. But the agency could go after any recent buyers of GM assets if the PBGC ended up with GM's pension obligations.

GM has also said it considers its pension plans to be fully funded, although obligations to provide health care coverage to its retirees and their family members are a drag on the company's results. But those health care obligations are not guaranteed by the PBGC.

GM is also holding talks with Nissan (Charts) and Renault, two overseas automakers that own stakes in one another, about possibly joining that alliance.

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