Resistance to General Motors Corp.'s (GM) bankruptcy plans is beginning to take shape as groups that stand to lose in the auto maker's restructuring begin maneuvering to get a better deal.

Three days into the auto maker's landmark bankruptcy case, lawyers on behalf of retirees and dealers are arguing the groups are being treated unfairly and are seeking separate representation. Meantime, hundreds packed a Manhattan hotel ballroom on Wednesday for a meeting in which the U.S. court trustee appointed a committee to represent unsecured creditors in Chapter 11 proceedings.

The 15-member committee includes the Wilmington Trust Co.; the United Auto Workers union; and the Pension Benefit Guarantee Corp., which is the federal agency that backstops corporate pensions, according to court documents. Others include GM dealers, suppliers and other unions.

Absent from the group is anyone representing large institutional bondholders, a majority of which agreed to accept 10% equity in a restructured GM in exchange for forgiving $27 billion in debt.

GM is looking to shutter thousands of dealerships, slash its debt and reduce labor costs as part of plans developed under close watch of the Obama administration. GM, which filed for bankruptcy protection Monday, said it was the only hope for the company that has lost nearly $90 billion since 2004.

The auto maker has expressed confidence that the support it received from bondholders last week will be enough to get court approval of what's known as a 363 sale of money-losing part of the business, even as some dissident bondholders work to derail the process.

Over the weekend, 54% of bondholders agreed to GM's 10% equity offer and promised not to fight GM on the sale. However, a judge would still need to sign off on the deal over what will likely be plentiful objections from bondholders who didn't agree.

As the official creditors' committee gets to work, other parties are looking to win separate recognition to help their chances on winning a better deal in court.

Former U.S. Attorney G. Douglas Jones said Wednesday he is asking the judge overseeing GM's case to enlist a committee to represent the interests of hundreds of auto dealers the auto maker seeks to close. Jones said he received a reply from GM indicating the auto maker felt all creditors could be dealt with in a single committee.

The auto maker on Tuesday sent letters to the dealers that are marked to close, offering them from $100,000 to $1 million to shut down without a fight, according to a dealer who received the letter.

The General Motors Retirees Association also asking the judge overseeing GM's bankruptcy to appoint a separate committee so they can negotiate with the company and protect their interests. GM's non-union retirees are arguing that their health benefits are at risk and they lack the protections of unionized workers.

-By Sharon Terlep; 248-204-5532; sharon.terlep@dowjones.com.