The repeal proposal, which will be filed in the Federal Register on Tuesday, fulfills a promise President Trump made to eradicate his predecessor’s environmental legacy. Eliminating the Clean Power Plan makes it less likely that the United States can fulfill its promise as part of the Paris climate agreement to ratchet down emissions that are warming the planet and contributing to heat waves and sea-level rise. Mr. Trump has vowed to abandon that international accord.

It also is a personal triumph for Mr. Pruitt, who as Oklahoma attorney general helped lead more than two dozen states in challenging the rule in the courts. In announcing the repeal, Mr. Pruitt made many of the same arguments that he had made for years to Congress and in lawsuits: that the Obama administration exceeded its legal authority in an effort to limit greenhouse gas emissions from power plants. (Last year, the Supreme Court blocked the rule from taking effect while courts assessed those lawsuits.) A leaked draft of the repeal proposal asserts that the country would save $33 billion by not complying with the regulation and rejects the health benefits the Obama administration had calculated from the original rule.

Coal- and natural-gas-fired power plants are responsible for about one-third of America’s carbon dioxide emissions. When the Clean Power Plan was unveiled in 2015, it was expected to cut power sector emissions 32 percent by 2030, relative to 2005. While many states are already shifting away from coal power for economic reasons, experts say scrapping the rule could slow that transition.

Environmental groups and several states plan to challenge the repeal proposal in federal courts, arguing against Mr. Pruitt’s move on both scientific and economic grounds.

Industry groups cheered the announcement, but have also indicated that they would prefer that Mr. Pruitt replace the Clean Power Plan with a new, more modest regulation on power plants in order to blunt any court challenges. The E.P.A. is still required to regulate greenhouse-gas emissions because of a 2009 legal opinion known as the endangerment finding.