CHICAGO – Illinois’ largest union and Gov. Pat Quinn’s administration reached a tentative contract agreement Thursday, averting the threat of the first strike by state workers in decades of collective bargaining.

The deal means that members of the American Federation of State, County and Municipal Employees Council 31 will get promised 2011 pay increases on which the Democratic governor reneged last year, according to a member of AFSCME’s bargaining committee. The member spoke on condition of anonymity because of not being authorized to speak publicly about the deal.

Neither the governor’s office nor union officials would publicly disclose details of the three-year agreement.