President Donald Trump has signed an executive order rolling back Obama-era rules aimed at curbing climate change.
The president said this would put an end to the “war on coal” and “job-killing regulations”.
The Energy Independence Executive Order suspends more than half a dozen measures enacted by his predecessor, and boosts fossil fuels.
Business groups have praised the Trump administration’s move but environmental campaigners have condemned it.
Outside the White House, a few hundred protesters gathered to vent their displeasure at the executive order.
Inside, the president was flanked by coal miners as he signed the order, saying: “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.”
During the campaign, he vowed to pull the US out of the Paris climate deal agreed in December 2015.
While campaigning for the presidency, Mr Trump argued that the agreement was unfair to the US.
The landmark agreement commits governments to moving their economies away from fossil fuels and reducing carbon emissions to try to contain global temperature rise.
Mr Trump has in the past said climate change had been “created by and for the Chinese”.
But at the end of last year, he acknowledged that there was “some connectivity” between human activity and climate change.
It is now unclear where exactly the US stands in relation to the deal.
Whatever the US chooses, the EU, India and China say they will stick to their pledges made in Paris.