President Donald Trump announced America's shock withdrawal from the Paris climate accord on Thursday, prompting a furious global backlash and throwing efforts to slow global warming into serious doubt.
In a sharply nationalistic address from the White House Rose Garden, Trump announced the United States would immediately stop implementing the "bad" 195-nation accord.
"I cannot, in good conscience, support a deal that punishes the United States," he said, decrying the "draconian financial and economic burdens the agreement imposes on our country".
Trump repeatedly painted the pact - struck by his predecessor Barack Obama - as a deal that did not "put America first" and was too easy on economic rivals China, India and Europe.
"I was elected to represent the citizens of Pittsburgh, not Paris," he said. "We don't want other leaders and other countries laughing at us anymore. And they won't be."
Trump offered no details about how, or when, a formal withdrawal would happen, and at one point suggested a renegotiation could take place.
"We're getting out but we'll start to negotiate and we will see if we can make a deal that's fair. And if we can, that's great. And if we can't, that's fine," he said.
That idea was unceremoniously slapped down by furious allies in Europe, who joined figures from around the United States and the world in condemning the move.
"The agreement cannot be renegotiated," France, Germany and Italy said in a joint statement.
'Reject the future'
The United States is the world's second largest emitter of greenhouse gases after China, so Trump's decision could seriously hamper efforts to cut emissions and limit global temperature increases.
Amid Trump's domestic critics was Obama, who said the United States was "joining a handful of nations that reject the future."
Nicaragua and Syria are the only countries not party to the Paris accord, the former seeing it as not ambitious enough and the latter being racked by a brutal civil war.
Hillary Clinton, Trump's opponent in last year's White House race, called the decision to pull out an "historic mistake".
"The world is moving forward together on climate change. Paris withdrawal leaves American workers & families behind," she said in a tweet.
Watch: 'US climate deal withdrawal is a mistake': Macron
Obama insisted that US business, state governors and mayors of major cities would step up.
The Democratic governors of New York, California and Washington states indeed formed a quick alliance, vowing to respect the standards agreed on under the Paris deal.
With much of the implementation of the accord taking place at the local level, the Paris accord's supporters hope the deal will be in hibernation rather than killed off entirely.
Trump's decision is likely to play well with the Republican base, with the more immediate damage on the diplomatic front.
The US president called his counterparts in Britain, Canada, France and Germany to explain his decision.
But traditional US allies were uncharacteristically blunt in their condemnation of the move, which comes amid already strained relationships with the hard-charging president.
Germany said the US was "harming" the entire planet, and European Commission President Jean-Claude Juncker called the decision "seriously wrong."
Ever the showman, the 70-year-old Trump had given his decision a reality TV-style tease, refusing to indicate his preference either way until his announcement.
Opponents of withdrawal - said to include Trump's daughter Ivanka - had warned that America's leadership role on the world stage was at stake, along with the environment.
A dozen large companies including oil major BP, agrochemical giant DuPont, Google, Intel and Microsoft, had urged Trump to remain in the deal.
Watch: UN's 'major disappointment' on US climate pact decision
Ultimately, the lobbying by Trump's environmental protection chief Scott Pruitt and chief strategist Steve Bannon urging the president to leave won out.
In the wake of the announcement, Tesla and SpaceX boss Elon Musk and Disney chief Robert Iger announced they would no longer take part in presidential business councils.
"Climate change is real. Leaving Paris is not good for America or the world," Musk said.
GE head Jeff Immelt said he was "disappointed" with the decision: "Climate change is real. Industry must now lead and not depend on government."
White House officials acknowledged that under the deal, formal withdrawal may not take place until after the 2020 election.
Hours ahead of Trump's announcement, China's Premier Li Keqiang pledged to stay the course on implementing the climate accord in a joint press conference with German Chancellor Angela Merkel, and urged other countries to do likewise.
China has been investing billions in clean energy infrastructure, as it battles to clear up the choking pollution enveloping its cities.
China and the US are responsible for some 40 per cent of the world's emissions and experts had warned it was vital for both to remain in the Paris agreement if it is to succeed.
The leader of Asia's other behemoth, Indian Prime Minister Narendra Modi - who is due to visit the White House shortly - has said failing to act on climate change would be "morally criminal".
Watch: Canada slams US climate pact decision
Trump's announcement comes less than 18 months after the climate pact was adopted in the French capital, the fruit of a hard-fought agreement between Beijing and Washington under Obama's leadership.
The Paris Agreement commits signatories to efforts to reduce greenhouse gas emissions that cause global warming, which is blamed for melting ice caps and glaciers, rising sea levels and more violent weather events.
They vowed steps to keep the worldwide rise in temperatures "well below" two degrees Celsius from pre-industrial times and to "pursue efforts" to hold the increase under 1.5 degrees Celsius.
Watch: India 'still committed' to Paris agreement
Watch: Trump's full speech