The largest rail union in the United States said on Tuesday it intends to oppose Union Pacific's proposed $85 billion acquisition of smaller rival Norfolk Southern in regulatory proceedings, citing concerns about how the largest-ever buyout in the sector will affect U.

Union Pacific said on Tuesday it would buy smaller rival Norfolk Southern in an $85-billion deal to create the country’s first coast-to-coast freight rail operator and reshape the movement of goods fr...

The merger would create the United States’ first coast-to-coast rail network, spanning 50,000 miles and 43 states.