A separate group holding 15 percent of the bonds outstanding, which had accepted the previous offer, also was expected to accept the sweetened deal.
In a Securities and Exchange Commission filing Thursday, GM said the equity stake of the bondholders would be "substantially reduced or eliminated" if enough of them did not accept the deal.
But a group representing smaller bondholders rejected the latest offer, saying, "the U.S. government appears to overtly favor the [United Auto Workers] members over America's seniors and retirees."
Under a revised labor contract overwhelmingly approved by union members Friday, the UAW's retiree health care trust would receive 17.5 percent of the new GM in exchange for about $10 billion in debt owed to it. The trust would be able to buy an additional 2.5 percent stake if the company's market value reached $75 billion.
UAW President Ron Gettelfinger said the union was not counting on that happening.
The U.S. government would receive an initial 72.5 percent stake in GM. The Canadian government is expected to provide GM with about $9 billion in financing in exchange for an undisclosed amount of equity.
