The administration of U.S. President Joe Biden is preparing to propose limits on greenhouse gas emissions from coal- and gas-fired power plants that are so stringent they could almost wipe out the U.S. electricity sector’s planet-warming pollution by 2040.

The White House is in the final stages of reviewing a draft proposal from the Environmental Protection Agency that would target both new and existing power plants — the second-biggest source of greenhouse gas emissions in the U.S. today. Details of the measure, some of which were previously reported by the New York Times, were described by people briefed on the plan.

The proposal, which could be unveiled in coming days, is the EPA’s second attempt to clamp down on carbon dioxide released from power plant smokestacks. The Supreme Court last year tossed out a sweeping Barack Obama-era rule that sought to shift electricity generation from fossil fuels toward renewable sources.