NEW YORK (Reuters) -Acting U.S. Labor Secretary Julie Su on Wednesday encouraged Boeing ( BA ) and more than 30,000 of the planemaker's factory workers to bridge a divide in negotiations and reach a fair contract, as a vote on a new deal looms on Sept. 12.

Boeing's ( BA ) Seattle-area workers, who produce the planemaker's strongest-selling 737 commercial jet, are voting next week on their first new contract in 16 years, with the two sides still tackling demands such as job security.

The workers can strike as early as Sept. 13 if they reject the contract and overwhelmingly support a work stoppage.

The U.S. planemaker has been seeking to restore 737 MAX production to a rate of 38 per month after a January mid-air panel blowout on a new plane led Boeing ( BA ) to slow output of the jet.

The union wants Boeing ( BA ) to commit to job security by providing guarantees that the next airplane program will stay in Washington state's Puget Sound area.

"We fully support collective bargaining," Su told Reuters on the sidelines of a New York convention held by the International Association of Machinists and Aerospace Workers which represents the Boeing ( BA ) workers. "I would just continue to encourage the parties to bargain, like they're not quite there, and that reaching a fair contract is a good thing."

"It's the way to allow everyone to then march forward together to accomplish the mission of the company in a way that prioritizes the workers," she added.

Boeing ( BA ) has more than 66,000 employees who live and work in Washington state on programs like the MAX, 767 and 777 widebody jets, representing the largest percentage of the company's global workforce.

U.S. unions have capitalized on tight labor markets to win hefty contracts at the bargaining table, with mainline pilots, autoworkers and others scoring big raises in 2023.

The IAM has asked for better retirement benefits, a seat on Boeing's ( BA ) board and wage increases exceeding 40% over three to four years after what it termed years of stagnant earnings.

"We remain confident we can reach a deal that balances the needs of our employees and the business realities we face as a company," Boeing ( BA ) said in a statement on Wednesday.