Machinists who have issued a strike notice to McDonnell Douglas Corp. will vote Sunday on the company’s latest contract proposal.

If members of International Association of Machinists District 837 reject the proposal, they will begin preparing for a strike that would idle 6,700 workers in the St. Louis area beginning Wednesday.

Workers predicted Thursday the union would reject the offer now on the table. The current proposal includes provisions for raises and pension benefits but doesn’t address the subcontracting of work to other companies, known as outsourcing.

The union is upset about McDonnell Douglas’ increasing use of outside contractors and the transfer of work to non-union plants in other cities, saying the moves are costing union members their jobs.

The two sides continue to talk. McDonnell Douglas is hopeful that negotiators can make enough progress by Sunday to head off a walkout, spokesman Tom Williams said.

The union issued a seven-day strike notice to the company on May 29.