Major unions on Tuesday slammed plans for an $85 billion merger between railway giants Norfolk Southern and Union Pacific.

As The New York Times reported, the proposed merger would have the benefit of creating the first rail network in the U.S. that would span from coast to coast and would run through 43 different states by linking Norfolk Southern’s eastern railroads with Union Pacific’s western rail network.

On the downside, however, it would represent a massive consolidation of the American rail industry by giving one corporation control of roughly 40% of rail freight throughout the U.S., and it was immediately panned by labor leaders as bad for railway workers.

SMART Transportation Division (SMART-TD), America’s largest railroad operating union, said that “our labor organization has every intention to oppose this merger when it comes before the Surface Transportation Board for approval.”