Union Iron Workers, after working more than three weeks without a new contract, walked off the job in much of Minnesota and Wisconsin Monday.

Charles E. Witt, business manager for Iron Workers Local 512, said employers represented by Associated General Contactors of Minnesota were refusing to negotiate until the union commits to pension concessions. Witt said members continue to work on projects covered by project labor agreements, but are "withholding services" on all other projects.

The job action falls short of a full strike only in that Iron Workers are not staffing picket lines that could keep other Building Trades unions off the job as well. Witt said Local 512 would set up pickets only if contractors try to bring in other workers to do the union's work.

The contract standoff affects as many as 1,600 members of Local 512 in most of Minnesota and 21 counties in western and north-central Wisconsin. Witt said contractors refused to give the union any contract proposals during mediated bargaining sessions on May 13 and May 18. The previous contract expired April 30.