Fresno County's largest labor union gave notice Wednesday that it will strike in protest of recent pay cuts, setting the stage for some 4,100 workers to walk off the job for three days starting Monday.

The move, which follows months of acrimony between county management and the Service Employees International Union, threatens to disrupt many public services.

Social programs, such as child support, food stamps and welfare, as well as libraries and administrative offices face potential hitches. So does the jail and juvenile hall, where most correctional officers are represented by the union.

County managers said late Wednesday they had a contingency plan in place to assure that essential services, including public safety, would be maintained.

They were yet to notify the departments of the strike, having just received notice.

"The union has been threatening this for a long time. Each of the departments should be ready," said county Personnel Director Beth Bandy.

Union officials declined to comment. But in a letter sent Wednesday evening to County Administrative Officer John Navarrette, SEIU local chapter Director Tom Ab-shere cited "unfair labor practices" as the reason for striking.

Last month, union workers were subject to a 9% pay cut or higher, and pleas to reconsider the reduction went unheeded by county managers.

Management has insisted that concessions are necessary to help balance the county's budget. Other county employees also have seen wage cuts and many have been laid off.

The union's case got a boost Wednesday when the state labor board issued a complaint against Fresno County for unfairly negotiating with employees.

The complaint, which came after the union filed a grievance with the California Public Employee Relations Board, accused the county of improperly forcing concessions on workers, not giving labor talks time to work out and interfering with employee protests.

A meeting in Sacramento has been set for next Thursday for the two sides to work out their differences in the presence of state moderators.

County officials denied the accusations, contending they've spent months trying to work with the union, and said they would be vindicated at next week's hearing.

Supervisor Debbie Poochigian was disappointed by news of the strike.

"I guess they got to do what they got to do," she said Wednesday, underscoring that the county would be prepared for the disruption.

SEIU represents about two-thirds of the county work force, which totals about 6,000.

Other unions represent some of the other county employees, and it wasn't clear Wednesday night whether other workers will choose to honor the picket line.

The last time the local chapter of SEIU went on strike was 1997, when about 1,000 employees were off the job for six days.

Union officials credited that action with forcing the county to return to the bargaining table and renegotiate.

They're hoping for the same outcome after next week's move.

The walk-off is scheduled to begin at 6 a.m. Monday and proceed until 10 p.m. Wednesday.