Nearly a month into a union walkout, the aerospace giant withdrew its latest contract offer, and the two sides exchanged blame over the breakdown.

Boeing has withdrawn a contract offer that would have given striking workers 30% raises over four years after talks broke down.

Boeing on Tuesday said that it has withdrawn its pay offer after negotiations with the International Association of Machinists and Aerospace Workers (IAM), whose members are on a strike against the company.

The company pulls an offer to striking workers as its financial woes mount and its planes get another safety warning.

Negotiations broke down between Boeing and its largest union, eroding hopes of a quick end to a strike that has halted production of most airplanes. Boeing shares fell 3.4% Wednesday after the company and the union accused the other of refusing to budge late Tuesday.

Boeing said late on Thursday it had filed an unfair labor practice charge with the National Labor Relations Board against the union representing its striking U.S. West Coast factory workers, accusing the leaders of not bargaining in good faith.

After negotiations broke down again between striking Boeing machinists and the aerospace giant, the leader of the union representing the workers says they are prepared to play the long game.