With the help of the BIW-built machines, Guilford-based Puritan Medical Group will double its monthly swab production from 20 million to 40 million.

BIW’s final three-year contract offer includes an annual 3% pay increase, maintains current premiums on benefits including 401(k) and life insurance but would increase health plan co-pays. A union committee has rejected the proposal, putting negotiations in flux.

Workers held a demonstration Wednesday morning to show solidarity as union officials negotiate for higher wages, among other demands.

While a strike hasn’t been declared yet, the union plans to hold a rally outside the union hall on Washington Street in Bath on Wednesday at 6 a.m.

“If BIW doesn’t cease its union-busting tactics and come back to the table with a suitable offer, our membership will likely have no other option but to strike,” Chris Weirs, president of Local S6, BIW’s largest union, wrote Monday. “The last thing we want is a strike, but we are prepared to do so if needed.”