Negotiators for West Chicago High School District 94 and its teachers union will meet at least twice more before teachers legally can strike, but contract talks have grown increasingly tense after nearly two years at the table.

Teachers this week filed a 10-day notice of their intent to strike. The filing with the district, the regional office of education and a state labor board allows union members to walk off the job as early as Feb. 12.

A spokeswoman for the Illinois Education Association said teachers have not yet set a strike date.

Teachers voted on Friday to authorize a strike and agreed to enter into a lease for a potential strike headquarters in downtown West Chicago. The vote by 129 association members was "without opposition," Union President Brad Larson said.

The strike threat comes less than a month after the union declared an impasse in contract talks that have failed to produce agreement on salaries, health benefits and other key sticking points.

Larson said Wednesday the association will bring a new salary proposal to the table when the two sides resume talks Feb. 7. Another session is set for Feb. 12.

Larson said he hopes the meetings are "productive."

"Nobody here wants to go on strike," he said. "All of our teachers want to be able to continue doing their jobs and to have the association and the board of education reach a fair settlement that can be ratified by the membership."

Nearly 2,100 students could be left out of classes should teachers strike for the first time since 1984. School board President Gary Saake said the district is making arrangements with park districts and libraries in Carol Stream, Winfield and West Chicago to offer programming in the event teachers walk picket lines.

The school board will hold a special meeting Thursday night to discuss negotiations in closed session after taking public comment. No action is expected, Saake said.

Saake said he's "hopeful, but not optimistic" about reaching a settlement "based on the action's of the association thus far."

In addition to the slow pace of the talks, he cited a decision by the union at the start of the school year to suspend volunteer sponsorship and coaching of student organizations and teams.

The impasse filing with the Illinois Educational Labor Relations Board forced the two sides to exchange contract offers. Negotiators still could not broker a deal by a Jan. 23 deadline, triggering the public posting of both proposals on the labor board's website.

During a session Jan. 22, the school board presented a new wage offer that would increase salaries for union members by an average of roughly 12 percent over four years.

Union negotiators said they are seeking an average 17 percent salary increase over the course of a four-year contract.

The board and the union started preliminary contract discussions in April 2016. The board last April presented a full proposal with a new salary structure based on a conceptual agreement with the union. The union delivered its own proposal two months later.

At a June meeting, the board offered nearly three dozen possible dates to meet over the summer, Saake said. The board's bargaining team later agreed to a union request to meet twice on two dates not included in that list, Saake said.

Teachers have been working under the terms of a one-year contract extension that expired in August.

The union is asking for so-called step increases, while the board "is focused on a salary formula based on the consumer price index to determine the cost of each teacher's salary individually," according to a statement released by the Illinois Education Association.

"The formula is not designed to retain teachers because (association) members would earn smaller annual salary increases the more years they work," the statement read.