Donald Trump's administration has officially told the United Nations that the US intends to pull out of the 2015 Paris climate agreement.
The US State Department made the announcement late on Friday afternoon.
It does not formally start the process of the US getting out of the voluntary agreement.
Still, the department describes its communication as a "strong message" to the world.
The director of US climate diplomacy during the Clinton and George W. Bush administrations, Nigel Purvis, said countries cannot withdraw from new international agreements, including the Paris climate one, until three years after they go into effect.
The Paris agreement went into effect on November 4 2016.
Then the process takes a year.
The State Department says it can officially start withdrawing as soon as November 2019.