A United Auto Workers union retiree health-care trust reportedly will receive a 17.5% stake in a restructured General Motors Corp., a much smaller share than the auto maker previously offered.

Last month, GM said it would give the UAW-managed trust, or Voluntary Employee Beneficiary Assn., a 39% stake in return for paying half of the $20 billion due to the fund.

That plan also called for the U.S. Treasury Dept., which has provided GM with $19.4 billion in taxpayer loans since the beginning of the year, to receive a 50% stake in the new GM. Bondholders carrying $27.2 billion in debt would get a 10% stake if at least 90% of them exchanged their bonds for equity.

However, the UAW tentatively is agreeing to take roughly half of the previous 39% stake, according to The Associated Press. In addition to the common shares, the UAW’s trust will receive $6.5 billion in preferred shares and a $2.5 billion note to fund the trust. The UAW’s stake in GM could grow to 20%.

GM also will offer another attrition program sweeter than the most recent round of buyouts if the auto maker’s 61,000 blue-collar workers ratify the deal later this week, The AP says. Several other news agencies report similar details, citing a summary of the UAW agreement reached last week and distributed to union leaders meeting today ahead of the vote.

As of midday, GM makes no announcement of reaching an equity-stake agreement with Treasury, and the outcome of its bond exchange ahead of a midnight deadline appears grim.

Bondholders have roundly rejected the 10% equity stake and countered recently with an offer to take 50%. GM President and CEO Fritz Henderson said on May 11 the Treasury would not consent to an offer to bondholders of more than 10%.

Talks between the Treasury and bondholders are ongoing today, according to various reports. Treasury spoke with bondholders at Chrysler LLC right up to the deadline, and the talks’ failure led to Chrysler’s bankruptcy.

GM could extend the bond exchange if it chooses. The auto maker faces a government-imposed deadline of June 1 to successfully restructure or enter bankruptcy.