The US on Monday formally notified the UN that it was withdrawing from the Paris climate accord, making the world's largest economy the sole outlier from the agreement.
US President Donald Trump went ahead with the pull-out despite mounting evidence of the reality and impact of climate change, with September the fourth month in the row with near- or record-breaking temperatures.
The US presented its withdrawal letter to the UN on the first possible date under the accord negotiated by Trump's predecessor Barack Obama.
It will be officially out of the Paris accord on November 4, 2020, one day after the US election in which Trump is seeking a second term on appeals to the white working-class.
Announcing the move, Secretary of State Mike Pompeo reiterated Trump's rationale in 2017 that the accord would disadvantage US businesses.
"It was America that would suffer the straitjacket," Pompeo told the Fox Business network. "It would be quintessentially unfair to the American people and to the American workers."
Pompeo said in a statement that the US would advocate a "realistic and pragmatic model" that included renewal energy but preserved a role for fossil fuels.
French President Emmanuel Macron, who unsuccessfully tried to persuade Trump to stay in the accord named for his nation's capital, lamented the decision.
"We regret this and it makes the Franco-Chinese partnership on climate and biodiversity even more necessary," the French presidency said as Macron visited China, the world's largest emitter of greenhouse gases blamed for climate change.
The US, the number-two emitter, is still planning to attend this month's COP climate negotiations in Spain, according to a State Department official.
Pompeo in his statement pointed to a 13 percent US reduction of greenhouse gas emissions from 2005 to 2017 even as the economy grew.
But Trump, who took office in 2017, has pledged to turn back environmental regulations as states such as California and New York try to take stronger action on their own.
Trump has sought to block California from setting tighter standards on car emissions and moved to let states set their own standards on existing coal-fired power plants.
Robert Menendez, the top Democrat on the Senate Foreign Relations Committee, said that the Trump administration has "once again thumbed its nose at our allies, turned a blind eye to the facts and further politicized the world's greatest environmental challenge".