Talks between Boeing Co. and its largest union to end an almost monthlong strike collapsed for a third time, extending a shutdown of the planemaker’s key commercial manufacturing base on the U.S. west coast.

Both the embattled planemaker and the International Association of Machinists and Aerospace Workers blamed each other for the impasse, following two days of mediated negotiations over a previously disclosed proposal that would have hiked wages 30% and boosted retirement benefits. Boeing said it has withdrawn the offer, saying further talks don’t make sense at this time.

Boeing and leaders for IAM District 751 have been in a stalemate over pay and pensions since the union’s 33,000 members walked off the job shortly after midnight on Sept. 13. “Unfortunately, the union didn’t seriously consider our proposals,” Stephanie Pope, who runs Boeing’s commercial airplane unit, said.

— Bloomberg