The union representing thousands of striking Boeing workers says a survey of its members shows they are "not interested" in the aviation giant's latest pay offer.
"Many comments expressed that the offer was inadequate," the International Association of Machinists and Aerospace Workers (IAM) said in a post on X.
It comes after Boeing made a new offer earlier this week to striking workers, which proposed a 30% pay rise over four years.
BBC News has requested a statement from Boeing in response to the IAM announcement.
"The survey results from yesterday were overwhelmingly clear, almost as loud as the first offer: members are not interested in the company's latest offer that was sent through the media," the IAM post said.
On Monday, Boeing made what it called its "best and final" pay offer, which included the reinstatement of a performance bonus, improved retirement benefits and a doubling of the value of a one-off bonus for signing a new pay deal to $6,000 (£4,470).
The company said the offer was dependent on it being ratified by union members by midnight pacific time on Friday 27 September (7:00 GMT on Saturday 28 September).
However, IAM said Boeing had sent the new offer directly to union members and the media without telling the union's representatives.
It also said the company's deadline did not give it enough time to organise a vote by its members.
Boeing denied that it had not informed IAM representatives about the offer, and said it would give the union more time as well as logistical support to ballot its members.
More than 30,000 Boeing workers have been on strike since 13 September after rejecting a 25% pay rise offer.
Union members - who produce planes including the 737 Max and 777 - voted overwhelmingly to reject the offer and back strike action until a new agreement could be reached.
IAM had initially aimed for a number of improvements to workers' packages, including a 40% pay rise.
The strike threatens to cost Boeing billions of dollars, deepening the crisis at a company already facing significant challenges.
The company has already suspended the jobs of tens of thousands of staff.
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