BATH, MAINE -- 05/13/15 -- Bath Iron Works' largest crane towers over the shipyard in Bath. Troy R. Bennett | BDN Credit: Troy R. Bennett

BATH, Maine — Leadership of the draftsmen’s union at Bath Iron Works has alerted its members that contract negotiations will be extended for another week, with the next meeting scheduled for Tuesday.

The two parties’ primary disagreement involves a flexible work week, according to social media posts from the union.

“As a condition of the extension, the BMDA has agreed not to engage in a strike and the company has agreed not to engage in a lockout prior to Sept. 24,” the Bath Marine Draftsmen’s Association, Local 3999 of the International Union of United Automobile Workers, posted on its Facebook page Monday morning.

According to the contract extension agreement, signed by union and company officials, the existing collective bargaining agreement was signed Sept. 16, 2013, and expired Sept. 17, 2017. The extension expires at 12:01 a.m. Sunday.

The proposed contract would expire March 20, 2022, according to official documents.

The union represents roughly 700 workers at the shipyard, which builds destroyers for the U.S. Navy Union members voted “overwhelmingly” on Saturday to authorize a strike after they rejected the company’s “last, best and final offer,” according to a post Sunday.

Union officials have contacted a federal mediator and planned to contact senior leadership of the UAW and Maine’s congressional delegation, officials wrote.

Union president Kirk Douglas on Monday declined to comment on the ongoing negotiations.

While some media portrayed the extension notice as a strike threat, it’s common practice for unions to take such a vote as part of its standard negotiating practices. The only time the union went out on strike was for three weeks in 1967, according to its website.

In December 2015, the largest union at Bath Iron Works — Local S6 of the machinists union — voted to accept a four-year contract that did not include pay raises but that did offer annual bonuses.

A BIW spokesman referred calls to Lisa Read, spokeswoman for General Dynamics, which owns Bath Iron Works. Read would only say Monday that the company is continuing negotiations.