Governor JB Pritzker is threatening to veto a bill that he says could raise costs for Ameren customers.
The bill approved by lawmakers last week would give the utility the right of first refusal to build high-voltage transmission lines, effectively given Ameren monopoly control over such lines.
The bill passed the Senate by a wide margin, but the margin was closer in the House, with more Republican votes than Democratic.
Pritzker says the bill benefits Ameren at the expense of consumers.
