A compromise to end the labor dispute that has left the city’s public school custodians without a contract for over two years was rejected Friday.

Members of AFSCME Local 287, the custodians’ union, turned down a contract negotiated by union leadership with City Hall by a vote of 92 to 50, sending the longstanding fight over the privatization of custodial services back to state arbitrators. It may take over a month for the three arbitrators, one selected by each side and the third agreed upon by both, to decide the outcome of the 25-month dispute.

“I am disappointed in the rejection of an offer which would have preserved 100 full-time jobs… while saving millions of taxpayer dollars,“ Mayor John DeStefano Jr. said in a press release.

The terms of the rejected contract, through 2015, would have eliminated bonuses, cut health benefits for new hires and increased required pension contributions while giving custodians raises for the next two years. Sean Matteson, DeStefano’s chief of staff, said in the release that the contract would have saved the city over $4 million in its first year.

If the city is successful in state arbitration, custodians face many more layoffs and the privatization of their jobs, which DeStefano has said will save the city up to $7 million.

The setback for AFSCME leaders comes amid ongoing closed talks among AFSCME’s state employee unions in the wake of their rejection of a labor agreement with Gov. Dannel Malloy.