With only weeks until a new mayor takes office, the Chicago school district has agreed to a union request to bring a mediator into contract negotiations.

Through an attorney, the district had tried to adjust the bargaining timeline agreed by two sides last August so that mayor-elect Lori Lightfoot could familiarize herself with negotiations. The union balked, arguing it was an attempt to push back the negotiations timeline.

In response, the district said it was agreeing to a mediator.

“In the interest of moving negotiations forward we have agreed to begin mediation,” the district said in a statement issued Monday.

Negotiating a new contract for the 21,000 teachers and support staff at district-run schools will fall to Lightfoot when she is sworn in on May 20. The union’s contract with the city expires on June 30.

In a speech to the City Club last week, union President Jesse Sharkey asked Lightfoot to speed up bargaining. He said the union is demanding a 5 percent pay raise that could be funded by raising taxes on the wealthy; increased benefits; a full-time nurse in every school; trained staff to help students dealing with trauma; and continuation of “community schools” that partner with local groups.

The union has suggested members stash away money and prepare for a strike this fall.

Meanwhile, teachers at five charter and contract schools are expected to walk out on Wednesday evening in the third charter teachers strike this school year.