President Donald Trump is pulling the US out of the world's first comprehensive deal on climate change, he has announced.
Mr Trump said the US would withdraw from the Paris Agreement, secured in the French capital in December 2015, which commits countries to curbing rising global temperatures.
But he also raised the possibility of negotiating to re-enter the Paris accord or an entirely new deal on terms that were "fair" to the US. The move drew widespread international criticism, with campaigners in the UK labelling it an "act of vandalism".
At a press briefing at the White House, Mr Trump said: "In order to fulfil my solemn duty to protect America and its citizens, the US will withdraw from the Paris climate accord."
The US would end the implementation of its voluntary commitments under the Paris Agreement to cut greenhouse gas emissions by 26% to 28% by 2025 compared with 2005 levels, and its contribution to climate finance, he said.
He said the deal allowed countries such as China and India to carry on polluting while the US economy was harmed, saying it was "less about the climate and more about other countries obtaining a financial advantage over the US".
But Mr Trump insisted he cared about the environment, and the US would be the most environmentally friendly country on Earth.
His predecessor Barack Obama, who signed the Paris Agreement last year without US Senate ratification, described the Trump administration as joining "a small handful of nations that reject the future" by withdrawing from the pact.
Only Nicaragua and Syria have failed to sign up to the agreement and all the major industrialised nations, except for Russia, have ratified it, with China and the EU set to affirm their commitment to deeper action on Friday.
Countries that stay in the Paris deal will "reap the benefits" of jobs and industries created and the US should be "at the front of the pack", Mr Obama said.
The hard-won deal commits countries to holding global temperature rises to "well below" 2C above pre-industrial levels, which will require emissions to be cut to net zero by the second half of the century.