The leaders of two of the nation’s biggest, most powerful labor unions — the Service Employees International Union [1] and the American Federation of State, County and Municipal Employees — are completing a plan that calls for unusually close cooperation in political campaigning, organizing and bargaining in states and cities across the United States. 

The effort begins a process that could lead to a merger of the two organizations, an outcome that would create the nation’s largest labor union, with some 3.6 million members. 

“While we recognize the differences in culture and structure between our respective organizations and the divisions that have hampered us in the past, the times demand that we build on our common purpose,” states a resolution the unions are expected to approve.

It cites challenges like political attacks on organized labor, growing income inequality and deteriorating workplace conditions. The document adds that the two unions will consider ways to step up the collaboration, including a formal merger. 

The resolution — which was adopted by the Service Employees International Union board on Thursday and was expected to be considered by the American Federation board in June — also would need to be ratified at conventions the unions have scheduled for this year.

The American Federation of State, County and Municipal Employees has 1.6 million members, most of whom are government workers. The Service Employees International Union has approximately two million members and is split nearly evenly between workers in the private and public sectors. About 80 percent of the unions’ membership is in roughly a dozen states, including New York, California and Illinois.

The purpose of the new arrangement, said Mary Kay Henry, the Service Employees International Union president, was to “unite the power of our organizations at every level to deal with the unprecedented attack on working people and growing inequality in this country.”