Speaking in Kentucky at a political event, EPA chief Scott Pruitt said he would tomorrow "be signing a proposed rule to withdraw the so-called Clean Power Plan of the past administration."
Pruitt said the rule, enacted in 2015, "was about picking winners and losers."
"The past administration was using every bit of power and authority to use the EPA to pick winners and losers and how we generate electricity in this country. That's wrong."
Prior to the finalisation of the rules in August 2015, "power plants were allowed to dump unlimited amounts of carbon pollution into the atmosphere," said the Union of Concerned Scientsts.
"No rules were in effect that limited their emissions of carbon dioxide, the primary driver of global warming."
The standards were developed under an act of Congress, called the Clean Air Act.