The Chicago Teachers Union and Chicago Public Schools are bringing in a mediator in an effort to iron out a new contract.

The CTU contract expired June 30. Mediation is a standard step in the negotiation process before a strike authorization vote can take place.

“We continue to look forward to productive conversations as we work toward an agreement that protects our classrooms, our teachers’ pensions and the taxpayers,” district spokeswoman Emily Bittner said. “Mediation is often productive in helping parties bridge their disagreements.”

Because the Chicago Teachers Union has deemed picking up all 7 percent of its pension costs at once as “strikeworthy,” Mayor Rahm Emanuel confirmed Wednesday that CPS CEO Forrest Claypool will propose stretching out the change over several years.

CTU spokeswoman Stephanie Gadlin said earlier this week that whether or not the pickup is gradual, it still equals “a pay decrease at a time when workloads have increased by more than 20 percent. Teacher compensation is a mandatory subject of bargaining and educators can determine to formally reject this demand and move to take a strike vote.”

The CTU has said during recent months of bargaining that they could accept no raises if the board considered some quality-of-life changes in classrooms.

The Sun-Times reported Tuesday that most nonunion CPS staffers will begin paying more toward their pensions at the end of the month and will pay a little more each year until they are making their entire 9 percent contribution within three years. The move is expected to save the district about $11 million a year once fully implemented.