Boeing withdrew a contract offer that would have given striking workers a 30 percent raise over four years after negotiations broke down.

The automaker said it strengthened its offer to union workers on take-home pay and retirement benefits during two days of negotiations.

“Unfortunately, the union did not seriously consider our proposals. Instead, the union has made non-negotiable demands that go far beyond what can be accepted if we are to remain competitive as a company,” Boeing said in a prepared statement. “Given this position, further negotiations do not make sense at this stage and our offer has been withdrawn.”

The union said it surveyed its members after receiving Boeing’s latest offer, and it was overwhelmingly rejected.

“Your bargaining committee attempted to address multiple priorities that could have led to an offer that we could put to a vote, but the company was unwilling to move in our direction,” the International Assn. said. of Machinists and Aerospace Workers District 751, said in a message to members.

The union complained last month that Boeing made public its latest offer to 33,000 striking workers without first negotiating with union negotiators.

The offer was more generous than the one that was overwhelmingly rejected when workers went on strike on September 13. The first proposal called for increases of 25%. The union initially demanded 40% over three years. Boeing said the average annual salary for machinists would increase from the current $75,608 to $111,155 at the end of the four-year contract.

The union represents workers at factories that assemble some of the company’s best-selling planes.

The strike continues as Boeing faces many other problems. It has stopped production of the 737, 777 and 767. Work on the 787 continues with non-union workers in South Carolina.

S&P Global Ratings placed Boeing Co. on its “CreditWatch Negative” list this week, citing increased financial risk due to the strike.

“We estimate that the company will experience a cash outflow of approximately $10 billion in 2024, in part due to the accumulation of working capital to support the overhaul of manufacturing processes and costs associated with the strike,” wrote S&P.

The addition of S&P’s CreditWatch system means there is an increased likelihood of a credit downgrade, which could make it more expensive for the company to borrow money.

Shares of Boeing, headquartered in Arlington, Virginia, fell nearly 3% at the open Wednesday and the stock is down 41% this year.