The Trump administration has issued its first written notification that the US intends to withdraw from the 2015 Paris climate agreement.
But in the notice to the United Nations the US state department said Washington would remain in the talks process.
President Donald Trump drew international condemnation in June when he first announced the US intention to withdraw.
He said the deal “punished” the US and would cost millions of American jobs.
Friday’s announcement is seen as largely symbolic as no nation seeking to leave the pact can officially announce an intention to withdraw until 4 November 2019.
The process of leaving then takes another year, meaning it would not be complete until just weeks after the US presidential election in 2020.
Any new US president could then decide to rejoin the agreement.