The National Park Service is calling a proposal for a $3.8 billion coal-fired power plant near Ely "unacceptable."
The federal agency says the plant would damage air and water quality, and interfere with scenic views in the vast Great Basin National Park.
The complaint was sent to the Nevada Division of Environmental Protection, which is considering a permit for the 1,500-megawatt Ely Energy Center.
The project is proposed by Sierra Pacific Power Company and Nevada Power Company.
A spokesman for the utilities calls the Park Service letter all part of the process.
The state could take six months or more before deciding on the Ely Energy Center air permit application.