The Trump administration has formally notified the United Nations that it will withdraw the United States from the 2015 Paris climate agreement, the first formal step in a one-year process to exit the global pact to fight climate change, US Secretary of State Mike Pompeo said on Monday.

The US, one of the world’s biggest sources of greenhouse gas emissions, would become the only country to leave the pact, a decision Trump promised to boost US oil, gas and coal industries.

Pompeo’s statement touted the US’s carbon pollution cuts and called the Paris deal an “unfair economic burden” to the US economy.

The State Department letter to UN Secretary-General Antonio Guterres started the clock on a process that would be completed one day after the 2020 US presidential election, on November 4, 2020.

While the move was expected, “we regret this and it makes the Franco-Chinese partnership on climate and biodiversity even more necessary”, President Emmanuel Macron said in a statement as he begins his visit to China.

Macron and President Xi Jinping will sign a joint document on climate during talks in Beijing on Wednesday that will declare the “irreversibility of the Paris accord”, the French presidency said.

Nearly 200 nations signed the climate deal in which each country provides its own goals to curb emissions of heat-trapping gases that lead to climate change.

The administration of former US President Barack Obama signed the US onto the pact, promising a 26-28 percent cut in US greenhouse gas emissions by 2030 from 2005 levels.

Trump campaigned on a promise to rescind that pledge, saying it would hurt the US economy while leaving other big polluters like China to increase emissions. But he was bound by UN rules to wait until Monday to file exit papers.