President Donald Trump declared the end of a "war on coal" Tuesday, as he moved to curb rules that underpin American emissions targets and a major global climate accord.

Following through on an election promise, Trump signed an order to review some of his predecessor Barack Obama's climate legacy, declaring an end to "job-killing regulations."

In a maiden trip to the Environmental Protection Agency, he ordered a review of emission limits for coal-fired power plants and eased up restrictions on federal leasing for coal production.

Trump said the measures herald "a new era in American energy and production and job creation."

Critics say that rolling back Obama's Clean Power Plan is unlikely to result in a boost to production or to create substantial numbers of jobs.

America's coal industry has long been in decline, with natural gas, cheap renewable energy, automation and tricky geology making the sooty fuel a less lucrative prospect.

In 2008 there were 88,000 coal miners in the United States, according to the US Energy Information Administration.

Today, the number of coal miners has fallen around 25 percent. More people work in Whole Foods, an upscale supermarket chain.

But some experts and environmental groups warned Trump's order could be the opening salvo of an effort to undermine internationally agreed targets under the Paris Climate Accord.

Curbing emissions from coal-fired power plants was a pillar of America's commitment to cut carbon emissions by 26-28 percent by 2025.

"It will make it virtually impossible" for the US to meet its target said Bob Ward, a climate specialist at the London School of Economics.

The Trump administration has not said whether it will pull out of the Paris deal.

"Whether we stay in or not is still under discussion," a senior administration official told AFP.

Energy giant Exxon Mobil has asked the Trump administration not to scrap US participation in the pact.

And veterans of the Obama administration played down the impact of Trump's actions.

Obama's former chief environmental advisor described the executive order as "terrible" but said "it isn't the ball game."

He added that any damage can be mitigated in the courts and in states, which are tasked with coming up with emissions reduction plans.

And "even if the Trump administration wants to pretend for the time being that climate change is not a big deal, people all over the world think it is a really big deal," said Todd Stern, who led US climate negotiators from 2009-2016.

Already the states of California and New York -- two of the most populous states -- have said they will press ahead with climate mitigation plans.

- Politics at play -

During the 2016 election campaign Trump donned a hard hat and embraced miners from Kentucky to West Virginia, promising to return jobs to long-ravaged communities. He won both states by a landslide.

Miners were by his side again on Tuesday. "Our incredible coal miners, we love our coal miners, great people," he said.

Trump's words may have been less well received in the corridors of the EPA's imposing Washington headquarters.

His repeated questioning of humans' role in warming the planet had prompted environmentalist critics to charge the fox is guarding the hen house.

Trump has done little to assuage those fears, vowing to slash EPA funding by a third, appointing anti-climate litigator Scott Pruitt as head of the EPA and Exxon's CEO Rex Tillerson as Secretary of State.

But Trump's climate skepticism has struck a chord with many Republican voters.

Some 68 percent of Americans believe climate change is caused by humans, but just 40 percent of Republicans say they worry about it, according to Gallup.

- 'War on coal' -

Some experts warn the economic payoff from abandoning Obama's 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 constant narrative about the 'war on coal' and the alleged devastating impact of EPA's regulations on West Virginia's coal industry will now be exposed for its inherent speciousness," he predicted.

Referring to the plan, the senior administration official told AFP: "It's going to take some time."

The United States is the world's second largest polluter. Around 37 percent of domestic carbon dioxide emissions come from electricity generation.

source: AFP