President Donald Trump ordered his energy secretary to take immediate action to stem power plant closures, arguing that a decline in coal and nuclear electricity is putting the nation’s security at risk.

“Impending retirements of fuel-secure power facilities are leading to a rapid depletion of a critical part of our nation’s energy mix and impacting the resilience of our power grid,” White House spokeswoman Sarah Sanders said in an emailed statement June 1. Trump has directed Energy Secretary Rick Perry...