The United States has formally exited the Paris accord to fight climate change a year after President Donald Trump notified the United Nations he would.
The world's largest economy and second-biggest greenhouse gas emitter after China is the first nation to quit the accord, which was signed by nearly all countries in 2015.
The move effectively puts the Trump administration at odds with all its allies and major competitors on the issue.
Trump has been a staunch opponent of the accord and has rolled back environmental regulations, saying they inhibit business and give other countries an edge.
He has repeatedly questioned climate change science.
The president first announced the US retreat in 2017. Should he be re-elected, the US would likely stay out of the international effort to slow climate change for at least the next four years.
Joe Biden, meanwhile, has vowed to immediately rejoin the Paris agreement if he wins the White House.
"Today, the Trump Administration officially left the Paris Climate Agreement. And in exactly 77 days, a Biden Administration will rejoin it," he wrote on Twitter on Wednesday evening, after expressing confidence in winning election.
Global reaction to the passing of the deadline was muted as the world watched with baited breath for the final results of Tuesday's US presidential election.
Germany said the US withdrawal was "highly regrettable," arguing that the European Union and Germany now had an even bigger duty to guard against global warming.
Chancellor Angela Merkel's spokesperson, Steffen Seibert, reaffirmed Germany's pledge to become climate-neutral by 2050, saying many countries and regions are moving towards a more climate-friendly economy, including several states, cities, municipalities, companies and organisations in the US.
International climate scientists warn drastic action is needed to prevent global temperatures rising more than 1.5 to 2 degrees above pre-industrial levels, as laid out in the accord.