The new rule, which is expected to come into effect within 30 days, assumes that the forces of the market will guide the country to a future of cleaner energy by naturally phasing out coal over time. It imposes only modest requirements on coal plants.

While it instructs states to reduce emissions, the new measure sets no targets. Instead, it lets states decide how much carbon reduction they consider reasonable and suggests ways to improve efficiency at individual power plants.

Jeffrey R. Holmstead, who served in the E.P.A. during both Bush administrations and now represents utility companies as a lawyer for the firm Bracewell, said he thought the current Supreme Court would be skeptical of any presidential effort to regulate carbon emissions under existing law.

“I t will establish what the E.P.A. can and can’t do,” Mr. Holmstead said of the new Trump rule. “I think it really will tie the hands of future administrations.”

Environmental groups say the Trump rule will slow the reduction of greenhouse gas emissions at a time when scientists warn that countries must rapidly decarbonize to avoid the most severe effects of climate change, including heat waves, extreme storms, droughts and floods.

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Mr. Wheeler has said the Trump administration’s plan is legally sound, will not damage the economy and will still go a long way toward reducing carbon .

He maintained that, when the new measure is fully implemented, it will reduce carbon emissions in the power sector by 34 percent below 2005 levels, roughly equal to the goals of the Clean Power Plan.