Philadelphia’s largest blue-collar union is on the verge of putting immense pressure on Mayor Cherelle Parker to resolve their contract dispute.

Members of AFSCME District Council 33, which represents more than 9,000 city workers, have authorized a strike that’s set to go into effect on Tuesday should the city and union not come to terms on a new deal for municipal workers.

The union – which represents workers in departments spanning sanitation and water, street maintenance and 911 operations – is set to walk off the job on Tuesday if a deal is not reached by the end of June.

Union leaders negotiated with the administration through the night before walking away shortly after 11 a.m. Monday without a new contract. The strike, which is expected to begin after midnight Tuesday, is a foregone conclusion as a result.

City officials held a press conference Monday afternoon to provide an update on the negotiations as well as response plans and operational readiness in light of a municipal work stoppage.