Updated from 2:57 p.m. EDT

A last ditch effort from federal mediators to get Boeing ( BA) and its labor unions back at the bargaining table failed Thursday afternoon when the company's management refused to continue negotiating.

"Preparation for these negotiations began nearly a year ago and included numerous meetings with union leadership and the union's negotiating team," Boeing said in a prepared statement. "The teams spent months negotiating in good faith. At the end of the scheduled talks, both sides had presented their final proposals and the process was ready to move to a vote. There is nothing left to negotiate."

Earlier in the day, federal mediators offered to extend the contract between Boeing and the International Association of Machinists and Aerospace Workers for another 30 days. Negotiations between management and the 26,000 employees represented by the IAM broke down earlier in the week, paving the way for a possible strike on Labor Day.

With Boeing's labor contract set to expire Sunday night, the Federal Mediation and Conciliation Service requested that Boeing and union representatives report to Washington, D.C. on Sept. 4 to resume contract negotiations. By extending the current contract, mediators were hoping to avert a costly strike at the world's largest airplane maker.

And so, IAM's membership will vote whether to strike starting this Monday. Had Boeing agreed to negotiate, the decision to extend the contract would have effectively prevented the strike for the next 30 days.

The union is calling for members to vote against accepting the contract on grounds that it doesn't provide enough in terms of pension benefits and job security. And in the wake of the most recent events, they're also calling on workers to vote in favor of the strike.

Three years ago, a similar situation occurred when the federal mediator's plea to return to the bargaining table fell on deaf ears. Workers from the Society of Professional Engineering Employees in Aerospace went on strike for 40 days until the matter was resolved.

Boeing has already presented workers with its "best and final" contract offer, which was rejected by unions on Tuesday evening and again Thursday, reaffirmed that position.

"We believe that IAM-represented employees should have the opportunity to vote on the contract offer," the company said. "Our position on the current offer remains unchanged; it is fair, it is competitive, and it allows us to better support our customers. This process should proceed in an open manner that respects the right of every voting employee."

Boeing ended Thursday's session down 36 cents to $37.17.

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