HARTFORD (AP) — Hundreds of Connecticut building cleaning workers who work in office towers and businesses voted Saturday to call a strike if a fair agreement is not reached on a new contract.

Officials with Local 32BJ of the Service Employees International Union said votes authorizing a strike were held in Hartford, New Haven and Stamford.

If agreements are not reached with local contractors, the workers could walk off the job after midnight on Dec. 31. That's when a contract expires for more than 4,000 cleaning workers throughout Connecticut.

More than 500 janitors in Hartford and New Haven voted unanimously at separate meetings to authorize a strike over a contract covering 2,400 workers in a region that stretches into New London. They clean 170 properties, including insurance company headquarters, malls, factories, universities and downtown office towers.

“Because of your unity and determination, there’s no question that we will win a good contract. It’s only a question of when we win,” 32BJ President Kyle Bragg told workers in Hartford. He had traveled from New York to speak to them on Saturday.

Hours later, video tweeted by the union showed hundreds of workers cheering “32BJ” in Stamford, where they also authorized the strike, if it becomes necessary.

Negotiations between the union and contractors began last month.