President Trump's environmental chief announced Monday he'll undo former President Obama's initiative to reduce emissions by power plants.
The Obama administration issued the plan in October, 2015, requiring coal-fired power plants to reduce carbon dioxide emissions by 32 per cent from 2005 levels by 2030.
Some experts say weakening the Clean Power Plan will not change the fortunes of the coal industry, which has lost significant share of US power generation to cheap, abundant USA natural gas.
The standards were developed under an act of Congress, called the Clean Air Act.
Mr Pruitt said he would sign the proposed rule to begin withdrawing from the plan on Tuesday.
Almost 200 countries have committed to combat global warming by reducing carbon dioxide and other greenhouse gases that contribute to global warming.
Climate and health experts say repealing the plan will increase health costs from air pollution and do little to limit greenhouse gas emissions, which the Supreme Court told the EPA to do in a 2007 decision, MA v. EPA.
The move by Trump's EPA is "a wholesale retreat from EPA's legal, scientific and moral obligation to address the threats of climate change", said Gina McCarthy, Obama's former EPA administrator.
Requirements that facilities use carbon capture technology or swap in natural gas for coal could actually come close to hitting the same goals as in Obama's Clean Power Plan - if not go even further, Schneider said. "They're using stall tactics to defer action, ignoring the courts and the demands of the American people".
Environmentalists have been sharply critical of Pruitt's repeal plan.
But trade organizations like the National Association of Manufacturers, which participated in a legal challenge to the plan, praised it.
"By saving an estimated 240 million tons of annual coal production, the administrator's action helps to safeguard more than 27,000 mining jobs and nearly 100,000 additional jobs throughout the supply chain", Hal Quinn, CEO of the National Mining Association, said in a statement.
New York Attorney General Eric Schneiderman (D), who is defending the Clean Power Plan in court, today promised to sue over the repeal.
The Clean Power Plan was never enforced.
Liz Perera, climate policy director for the Sierra Club, said repealing the Clean Power Plan "is about one thing and one thing only: helping corporate polluters profit".