General Motors Corp. (GM) told bondholders Thursday that they could be wiped out if they don't accept an offer for 10% of the restructured company by a Saturday deadline.

The new proposal contained in a regulatory filing envisages an initial 72.5% stake in a "New GM" being held by the U.S. Treasury in return for enhanced aid.

The company is expected to file for bankruptcy protection by Monday, and an ad hoc bondholders committee expressed support for the new offer Thursday.

Its union-run health trust would receive 17.5%, with 10% going to creditors - in line with the offer they rejected Tuesday - though warrants could lift this to 15%.

The Canadian federal government and the state of Ontario are both slated to receive some equity and preferred stock in return for debt financing.

The filing didn't mention existing ordinary shareholders, who were originally due to receive 1% in a 'New GM", though its shares rose 13% in early trade to $1.30.

As part of the deal, bondholders wouldn't oppose GM's plans, should it enter bankruptcy, to sell bad assets. Bondholders have until 5 p.m. Saturday to decide whether to accept the offer.

GM said an ad hoc committee representing institutional investors supported the terms. The group had previously said it would oppose such a move.

The company's U.S. workers are voting Thursday on contract amendments, while the German government has delayed until Friday a decision on supporting a partial buyout of the company's European operation.

-By Sharon Terlep, Dow Jones Newswires; 248-204-5532; sharon.terlep@dowjones.com