Missouri’s biggest power company is accusing the biggest railroad serving Missouri of getting in the way of supplying coal to its Labadie power plant.

Ameren Missouri says Union Pacific is blocking Missouri Central Railroad from serving the plant. A subsidiary of Ameren owns Missouri Central. Ameren wants to use Missouri Cenral to supply coal from Illinois instead of using Union Pacific to bring in coal from Wyoming. Union Pacific says its position does not violate any national transportation policies.

The federal Surface Transportation Board is trying to mediate the dispute.