The Chicago Board of Education has asked teachers, social workers and other union members to take a 7 percent pay cut in its upcoming contract, according to the Chicago Teachers Union, an opening move in negotiations that has sparked discontent among union members.

"The CTU is highly insulted,” CTU spokeswoman Stephanie Gadlin said.

Union president Karen Lewis said the Board of Education has made CPS "broke on purpose" and accused Mayor Rahm Emanuel of "laying in wait" to raise property taxes and expand charter schools.

"Once again, the Board has created a fiscal crisis in order to justify its continued attack on our classrooms and communities. CPS is broke on purpose," Lewis said in a statement. "By citing its so-called $1.5 billion deficit, the mayor is proposing a reduction in teaching staff which will result in larger class sizes and the loss of teaching positions."

Late last week, the board told the union it would not offer an optional fourth year of its existing contract that expires June 30, saying the district could not afford the $105 million in raises guaranteed in that deal.

CPS spokesman Bill McCaffrey could not immediately say how much money such a cut would save the district burdened with a $1.1 billion deficit and at least $9 billion in pension obligations.