In a major victory for labor, commercial building owners and several major security guard contractors announced Tuesday that they reached an agreement with the Service Employees International Union to allow the union to organize some 10,000 security guards in Los Angeles County.

The agreement between the Building Owners and Managers Association of Greater Los Angeles, which represents most of the commercial building owners in Los Angeles, five major security guard contracting firms and the SEIU ends a seven-year campaign by the union to force building owners to allow them to unionize security guards.

“The owners of the larger office buildings in Los Angeles have said, ‘We’re not going to resist this,’” said Martha Cox-Nitikman, senior director of government and public affairs for the L.A. chapter of the building owners’ association. “We’ve agreed to be neutral and to facilitate the negotiations.”

The agreement applies to all commercial office buildings over 75,000 square feet in the county. Further details of the agreement were not released. Representatives of the SEIU were not immediately available for comment.

The move comes 10 months after real estate mogul Robert Maguire, one of the largest office building owners in the county, reached a separate agreement with SEIU to allow the union to organize security guards at his buildings, mostly downtown.

But union efforts to reach agreements with the rest of the owners stalled. Building owners said they had concerns about allowing the SEIU, which already represents janitors, to also represent the security guards in office buildings. If one group decided to strike, the other group could honor that strike and threaten building operations.

Once building owners and the union agreed to insert language restricting such sympathetic strikes, the way was cleared for the agreement, Cox-Nitikman said.