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

Following through on an election promise, Trump on Tuesday signed an "energy independence" executive 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.

A coalition of 23 US states and local governments vowed to fight the order in court.

"These actions are an assault on American values and they endanger the health, safety and prosperity of every American," said billionaire environmental activist Tom Steyer, the head of activist group NextGen Climate.

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

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

The US 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. That number is now down 25 percent.

Christy Goldfuss, an energy expert at the Center for American Progress, said that whatever policy changes Trump makes, it is the markets that will decide what industry is viable.

"The executive order today is not going to bring back coal jobs," Goldfuss, who helped develop Obama's climate action plan, told Al Jazeera.

"The market is just not demanding coal here in the United States. The resurgence of natural gas is really driving our entire economy when it comes to energy right now, not to mention renewables that have come on board in a hugely affordable manner."

Paris Accord in question

Some experts and environmental groups also warned that Trump's order could be the opening salvo of an effort to undermine internationally agreed targets under the Paris Climate Accord, which was reached by nearly 200 countries in 2015.

Curbing emissions from coal-fired power plants was a pillar of the US' 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, of Trump's executive order.

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

Christiana Figueres, former executive secretary of the United Nations Framework Convention on Climate Change, who helped broker the Paris accord, lamented Trump's order.

"Trying to make fossil fuels remain competitive in the face of a booming clean renewable power sector, with the clean air and plentiful jobs it continues to generate, is going against the flow of economics," she said.

Already the states of California and New York - two of the most populous states - have said they will press ahead with climate mitigation plans despite Trump's moves. Both states are controlled by Democratic governors.

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

While some 68 percent of Americans believe climate change is caused by human beings, only 40 percent of Republicans say they worry about it, according to polling agency Gallup.

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