President Donald Trump on Thursday announced that the US is withdrawing from the 2015 Paris climate agreement.
He said moves to negotiate a new "fair" deal that would not disadvantage US businesses and workers would begin.
Trump said during last year's presidential election campaign that he would take the step to help his country's oil and coal industries.
Opponents say withdrawing from the accord is an abdication of US leadership on a key global challenge.
The Paris agreement commits the US and 187 other countries to keeping rising global temperatures "well below" 2C above pre-industrial levels and "endeavour to limit" them even more, to 1.5C. Only Syria and Nicaragua did not sign up to the deal.
What did Trump say?
Speaking in the White House Rose Garden, Trump characterised the Paris agreement as a deal that aimed to hobble, disadvantage, and impoverish the US.
He claimed the agreement would cost the US $3 trillion in lost GDP and 6.5 million jobs - while rival economies like China and India were treated more favourably.
"In order to fulfil my solemn duty to protect America and its citizens, the United States will withdraw from the Paris climate accord... but begin negotiations to re-enter either the Paris accord or a really entirely new transaction on terms that are fair to the United States," he said.
The speech contained several rhetorical flourishes reminiscent of his campaign speeches.
"We don't want other leaders and other countries laughing at us any more - and they won't be," he said.
"I was elected to represent the citizens of Pittsburgh, not Paris. I promised I would exit or re-negotiate any deal which fails to serve America's interests. Many trade deals will soon be under re-negotiation."
The BBC's Rajini Vaidyanathan in Washington says the move will be welcomed by many Trump supporters, as for them this is less about science - and more about sending a signal to so-called global elites.
Analysts say the US withdrawal from the Paris agreement will make it more difficult for the world to reach the goals that it set for itself in the Paris agreement.
The US contributes about 15 per cent of global emissions of carbon, but it is also a significant source of finance and technology for developing countries in their efforts to fight rising temperatures.
Trump did not give a timescale for US withdrawal, but White House sources had earlier suggested it could take up to four years.
Former US President Barack Obama, who agreed to the Paris deal, immediately criticised the move, accusing the Trump administration of "rejecting the future".
Republican congressional leaders and the US coal industry backed the move, with Senate Majority Leader Mitch McConnell supporting Trump "for dealing yet another significant blow to the Obama administration's assault on domestic energy production and jobs".
Senate Democratic leader Chuck Schumer called the decision "one of the worst policy moves made in the 21st Century because of the huge damage to our economy, our environment and our geopolitical standing".
The leaders of France, Germany and Italy issued a joint statement rejecting a renegotiation of the agreement.
"We deem the momentum generated in Paris in December 2015 irreversible and we firmly believe that the Paris agreement cannot be renegotiated, since it is a vital instrument for our planet, societies and economies," it said.
Canada was "deeply disappointed" by President Trump's decision, Environment Minister Catherine McKenna told reporters.
This was echoed by UK Prime Minister Theresa May, who expressed her disappointment and told Trump in a phone call that the deal protects the "prosperity and security of future generations".
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