The nation’s largest underground coal mining company is at odds with its power customers over retaining Obama-era toxic air pollution standards for power plants that analysts claim hurt the domestic coal market.

“We believe that the Trump Administration should completely rescind the Obama administration’s utility mercury and air toxics rule,” Murray Energy spokesman Gary Broadbent told Bloomberg Environment.

Murray Energy’s stance is at odds with a power sector that has spoken with one voice in favor of retaining the 2012 rule, known as the Mercury and Air Toxics Standards, or MATS, because it has already invested $18 billion to...