FILE PHOTO - U.S. Secretary of Energy Rick Perry gestures during a news conference in New Delhi, India, April 17, 2018. REUTERS/Adnan Abidi

BARILOCHE, Argentina (Reuters) - A plan requested by U.S. President Donald Trump to prevent struggling nuclear and coal power plants from shutting is still being “fleshed out” by the U.S. Department of Energy (DOE) and the White House, Energy Secretary Rick Perry said on Friday.

Trump on June 1 directed Perry to take emergency steps to keep nuclear and coal plants running, in what would amount to an unprecedented intervention in U.S. power markets that has drawn backlash from environmentalists as well as oil, gas and renewable energy companies.

“This is not just singularly an economic issue,” Perry told reporters at the G20 Energy Ministers’ meeting in Bariloche, Argentina, citing risks of cyberattacks by “nefarious actors” or “terrorist groups” on the civilian electric grid, which also provides U.S. military bases with nearly all their power.

According to the DOE, cyber and physical threats are “minimized” at nuclear and coal plants because they can store months of fuel on site to survive a supply cut. Some experts have said coal infrastructure is just as susceptible to cyber attacks as natural gas pipelines.

The U.S. coal and nuclear power industries have been shrinking for years, under pressure from cheaper natural gas along with advances in solar and wind energy.

“You would not want to wager that your liberties and your freedoms in a country - the United States in this case - should be left solely to the free market,” Perry said.

He did not respond to questions on when the plan would be announced or its details.