As President Donald Trump is deciding whether the USA should remain in the Paris climate deal, United Nations Secretary General Antonio Guterres is calling on the world to unite to fight the "unprecedented and growing threat" of climate change.
On Tuesday, he met with EPA administrator Scott Pruitt, who has denied the science behind climate change.
While travelling overseas last week, Trump was repeatedly pressed to stay in the deal by European leaders and the Vatican.
Almost 200 nations, including the US, agreed in 2015 to voluntarily reduce their greenhouse gas emissions. "If we can't, that's fine", he said. But he was also breaking from many of America's staunches allies, who have expressed alarm about the decision.
As any good reality TV star would, Trump teased the big reveal, tweeting Saturday that he would "make my final decision on the Paris Accord next week!"
The agreement was reached under the United Nations Framework Convention on Climate Change, which was ratified by the U.S. Senate in 1992. At the summit, German Chancellor Angela Merkel told reporters the climate debate was "controversial" and that the leaders of the other G7 nations - France, Japan, Canada, the United Kingdom and Italy - all urged Trump to remain a part of the 2015 agreement.
The Paris decision has deeply divided the Administration, with internationalists, such as Tillerson, arguing that it would be beneficial to the United States to remain part of negotiations and worldwide meetings surrounding the agreement, as a matter of leverage and influence.
He also pointed to the opportunities that climate action can provide, such as through the creation of jobs and increased economic growth.
Earth is likely to reach more unsafe levels of warming even sooner if the USA retreats from its pledge to cut carbon dioxide pollution, scientists said.More news: Trump to announce decision on global climate deal
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In Congress, 40 Democratic senators sent Trump a letter saying withdrawal would hurt America's credibility and influence on the world stage.
In his first major speech on climate action, Guterres promised that he will intensify high-level political engagement to "raise the bar" on climate action.
Soon after the news broke, an official from the European Union confirmed that the EU and China would "reaffirm" their committment to the deal despite the US' decision, AP reported.
"Disappointed by early reports that the USA will join Syria and Nicaragua as the only countries not party to the #ParisAgreement", tweeted Florida Republican Rep. Carlos Curbelo, who co-chairs the House Climate Solutions Caucus that includes 20 GOP and 20 Democratic lawmakers.
Interior Secretary Ryan Zinke said Wednesday in Alaska that he had "yet to read what the actual Paris Agreement is", and would have to read it before weighing in.
The head of the United Nations has a clear message for countries and companies dragging their feet on climate change: "Get on board, or get left behind".
California Governor Jerry Brown called Trump's decision possibly "tragic" and a step "backwards" for the US.
The United States, under former President Barack Obama, had committed to reduce its emissions by 26 percent to 28 percent from 2005 levels by 2025.
A decision is supposed to come this week on whether the United States will remain in the Paris climate change deal. Aides have been deliberating on "caveats in the language", one official said.
Trump has constantly claimed that there is no real evidence to prove that climate change exists, and has called it a "hoax".
He said 80 percent of the world's energy still comes from fossil fuels - oil, gas and coal - and that would not change overnight.