Donald Trump has rolled back Barack Obama's record on climate change with a series of orders undermining America's commitment to tackle global warming.
In his first trip to the Environmental Protection Agency (EPA) the President - who has called global warming "a hoax" created by China - has signed an Energy Independence Executive Order.
Kicking off what he called "the start of a new era in American energy", his instructions will allow regulators to rewrite key rules curbing US carbon emissions, lift a temporary ban on federal coal leasing and scrap a requirement for federal officials to consider the impact of climate change when making decisions.
Before signing the decree Mr Trump said: "My administration is putting an end to the war on coal.
"With today's executive action I am taking historic steps to lift the restrictions on American energy, to reverse government intrusion and to cancel job-killing regulations."
Central to the changes is a review of Barack Obama's clean power plan - a pledge to cut US emissions by 26-28% by 2025 - which paved the way for the Paris agreement on tackling climate change involving 195 countries.
A senior Trump administration official told the AFP news agency that the prospect of withdrawal from the Paris agreement was "still under discussion".
The White House said the measures will "help keep energy and electricity affordable, reliable, and clean in order to boost economic growth and job creation".
But environmentalists have warned that the White House's new measures will have serious consequences both at home and abroad.
Billionaire environmental activist and head of activist group NextGen Climate Tom Steyer said: "These actions are an assault on American values and they endanger the health, safety and prosperity of every American."
The president of green group Earthjustice, Trip Van Noppen, said: "This order ignores the law and scientific reality." The organisation has said it will be challenging the ruling in court.
Mr Trump's environmental views are very different to those of former president Obama, who said that climate change was "real and cannot be ignored".
The President has already vowed to slash EPA funding by a third and appointed Scott Pruitt - who previously sued the agency - as its head.
His pick of former Exxon chief executive Rex Tillerson as Secretary of State has also caused concern among environmental campaigners.
But Mr Trump's climate scepticism - and promises to bring back coal mining jobs to states such as Kentucky and West Virginia - appeared to strike a chord with Republican supporters on the campaign trail.
Around 68% of Americans believe climate change is caused by humans, but just 40% of Republicans say they worry about it, according to a Gallup poll.
Some experts have warned the economic benefit from ditching the clean power plan will be limited.
"In my view, it will have virtually no impact," said professor James Van Nostrand of West Virginia University, who said the decline of coal had more to do with higher mining costs and cheaper natural gas and renewables.
"Defunding or dismantling the EPA and repealing its regulations is not going to bring the coal industry back."
The US is the world's second largest polluter. Around 37% of domestic carbon dioxide emissions come from electricity generation.
Mr Trump has issued a series of executive orders since entering the Oval Office in January.
He would claim success for pulling the US out of the Trans-Pacific Partnership international trade agreement - which he saw as a "bad deal" for the country.
But his most controversial order - a travel ban on Muslim-majority countries - has twice been blocked by legal challenges.