NEW YORK (Reuters) - U.S. power firm Vistra Energy Corp said on Friday that it would shut two coal-fired plants for economic reasons, as closures in the industry continue apace despite the environment regulator saying this week he wanted to end the “war on coal.”

U.S. President Donald Trump turns to wave at a coal barge on the Ohio River as he delivers remarks on his potential infrastructure proposals during an event at the Rivertowne Marina in Cincinnati, Ohio, U.S. June 7, 2017. REUTERS/Jonathan Ernst

Vistra's VST.N subsidiary Luminant will close two Texas power plants, it said in a statement on Friday. The announcement came just a week after Luminant revealed the closure of a further Texas plant.

Together the three plants will remove more than 4,200 megawatts (MW) of coal-generated power, enough to supply electricity to more than four million homes.

Environmental Protection Agency Administrator Scott Pruitt said on Tuesday he wanted to ease pressure on the coal industry by scrapping a package of rules put in place under President Barack Obama, known collectively as the Clean Power Plan.

The plan had sought to reduce greenhouse gas emissions from power plants through a series of emissions caps. Fossil fuel companies and some states have said the regulations were too onerous and the plan was halted before it came into effect by the Supreme Court.

But the new closures show regulation is not the only pressure on coal. Cheap gas from record shale production over the past decade has made some older coal plants uneconomic, especially those that require costly upgrades to meet increasingly strict environmental rules, often imposed by states.

EPA officials had no immediate comment.

“It’s ironic that this news comes the same week the Trump administration chose to roll back the Clean Power rule that would have reduced power plant climate-altering pollution,” said Ilan Levin, Texas Director of anti-pollution pressure group the Environmental Integrity Project, in a statement on Friday.

The capacity of U.S. coal plants expected to shut in 2018 is now more than 13,600 MW compared with an expected 7,600 MW in 2017 and almost 13,000 MW in 2016. In 2015, power companies shut almost 18,000 MW of coal-fired generation, the most in any year.

Coal served as the primary fuel source for U.S. power plants for a century, but its use has been declining since a peak in 2007, around the same time drillers started pulling gas out of shale formations.

Gas became the leading power plant fuel in 2016 when the amount of coal used to produce electricity fell to its lowest level since 1982, according to federal data.