ST. LOUIS (AP) — A federal judge has blocked a proposed joint venture between two leading private coal companies.

The St. Louis Post-Dispatch reports that the ruling Tuesday by U.S. District Judge Sarah Pitlyk in St. Louis halts the proposed joint venture of two companies based in the St. Louis area, Peabody Energy and Arch Resources. Pitlyk wrote that the Federal Trade Commission “has shown that there is a reasonable probability that the proposed joint venture will substantially impair competition in the market for Southern Powder River Basin coal.”

In June 2019, Peabody and Arch proposed combining the country’s two most productive mines, which border each other in Wyoming.