The Trump administration has issued its first written notification that America intends to withdraw from the 2015 Paris climate agreement.
"Today, the United States submitted a communication to the United Nations in its capacity as depositary for the Paris Agreement regarding the US intent to withdraw from the Paris Agreement as soon as it is eligible to do so," the US statement read.
The note, a largely symbolic move, said Washington would remain in the talks process.
President Donald Trump said the deal "punished" the US and would cost millions of American jobs.
America is unable to officially announce its intention to withdraw until November 4, 2019.
The exit process takes a year.
If the withdrawal process is triggered at the earliest official stage, America would leave weeks after the US presidential election in 2020.
Whoever is the US president in that year could then decide to rejoin the agreement.