Environmental groups have sued federal officials over plans that would allow extensive oil, gas and coal development in the Powder River Basin of Montana and Wyoming.
The lawsuit against the Bureau of Land Management was filed Tuesday in U.S. District Court in Great Falls. It targets agency plans approved in September as part of efforts to protect greater sage grouse.
The lawsuit is backed by the Western Organization of Resource Councils, Sierra Club and other groups.
They say letting companies extract fossil fuels from millions of acres in the region would make climate change worse.
The Powder River Basin is the largest coal mining region in the U.S.
Bureau of Land Management spokesman Al Nash said the agency does not comment on pending litigation.