Contract talks have stalled between the Los Angeles Unified School District and the labor union representing more than 30,000 bus drivers, teachers aides, clerical workers, custodians and other "classified" employees in the school system, union leaders said Monday.

Sensing the two sides are making little progress toward a new contract, leaders of the Service Employees International Union Local 99 announced they will take one step closer to a strike over the next month.

SEIU Local 99 rank-and-file will vote on whether to authorize a strike between March 12 and March 24, casting ballots in person at hundreds of different school sites during that time. If they do authorize a strike, the union's bargaining team would be empowered to declare a strike "as early as this school year," union leaders said in a statement.

"There’s a lot of support— not support, but a lot of talk of strike right now," said the union's president, Max Arias. "People are fed up. That’s their sentiment."

Union leaders and the district have been bargaining over a new contract with L.A. Unified for the last year. The district has is engaged simultaneously in separate contract talks with other labor unions, including with United Teachers Los Angeles.

Arias said wages, work hours and staffing levels remain sticking points.

"There has been no movement from the beginning on wages," said Arias. He said the district's offer of a 2 percent raise and 7 extra working days — which, for employees who don't usually work year-round, essentially amounts to a one-time bonus — is essentially unchanged from its initial offer in April. (Arias declined to detail the union's counter-offer on wages.)

L.A. Unified's chief labor negotiator, Najeeb Khoury, called the district's wage offer "solid," but said the district had to take into account projections that show the district's budget is likely to get even tighter in coming years as benefits costs mount and student enrollment shrinks.

"We encourage SEIU Local 99," Khoury said, "to continue working with us at the table to find solutions that take into account our economic reality. We trust that SEIU Local 99 will follow the law and will not declare a strike before going through all the statutory mandated procedures, including mediation and fact-finding."

Arias acknowledged the district had offered a possible solution to a problem faced by special education assistants, which his union represents.

But on issues like staffing levels for janitors, the two sides remain far apart, Arias said. He said SEIU Local 99 wants to rebuild custodial staffs to pre-recession levels — which were already only half of what his union considered a "minimum" staffing level.

"It’s creating a condition in which bathrooms are closed, schools are not clean in many instances," Arias said.

Khoury said L.A. Unified offered to create a $1 million "cleanliness fund" and would allow for provisions that would allow for new negotiations should the district's budget forecasts improve.

"We value SEIU Local 99 as a labor partner," Khoury said, "and look forward to collaboratively finding solutions together."