The Trump administration has completed a detailed legal proposal to dramatically weaken a major environmental regulation covering mercury, a toxic chemical emitted from coal-burning power plants, according to a person who has seen the document but is not authorized to speak publicly about it.

The proposal would not eliminate the mercury regulation entirely, but it is designed to put in place the legal justification for the Trump administration to weaken it and several other pollution rules, while setting the stage for a possible full repeal of the rule. 

Andrew Wheeler, a former coal lobbyist who is now the acting administrator of the Environmental Protection Agency, is expected in the coming days to send the proposal to the White House for approval. 

The move is the latest, and one of the most significant, in the Trump administration’s steady march of rollbacks of Obama-era health and environmental regulations on polluting industries, particularly coal.