WASHINGTON — President Donald Trump will announce on Thursday whether the United States will withdraw from the Paris climate accord, as aides reportedly said a pullout is likely.

"I will be announcing my decision on Paris Accord, Thursday at 3:00 P.M. The White House Rose Garden. MAKE AMERICA GREAT AGAIN!" the US leader said in a tweet late Wednesday, punctuating the post with his populist campaign slogan.

Trump has not given any indication of which way he is leaning, saying he’d been "hearing from a lot of people, both ways. Both ways."

America’s international allies and Trump’s domestic opponents lashed out Wednesday at media reports that he had made up his mind to pull the United States out of the global accord to curb carbon emissions, a move that would make the deal less effective.

The White House did not confirm those reports and it was unclear whether Trump would fully scrap US participation or merely water down US emissions objectives.

An American withdrawal would come fewer than 18 months after the historic 196-nation pact was signed in the French capital -- the fruit of a hard-fought agreement between Beijing and Washington under Barack Obama’s leadership.

The European Union and China indicated they would press ahead with the deal, regardless of US participation.

The United States is the world’s second biggest carbon emitter, after China.

"China and the EU... will implement the agreement," a senior EU official told reporters on Wednesday, on condition of anonymity.

"The Paris Agreement will continue with full force of implementation even if the US pulls out."

Under Trump, who once called climate change a "hoax", the country has resisted intense pressure from its partners to commit to respecting the global accord.

The White House had previously indicated that Trump could simply recalibrate emissions targets.

Under Obama, Washington had pledged to reduce greenhouse gas emissions by 26-28 per cent below 2005 levels by 2025.

Nancy Pelosi, one of the top Democrats in Congress, described the apparent decision as a "stunning abdication of American leadership and a grave threat to our planet’s future".

Six against one 

Trump’s position on the Paris accord was a focal point of last week’s G7 summit in Sicily, at which leaders of the world’s six other leading economies pressed him to renew the US commitment to the deal.

A frustrated German Chancellor Angela Merkel later warned that Europe "must take its fate into its own hands," citing the differences with Washington on climate change as evidence of their divergent paths.

She described the discussion as "very difficult, not to say very unsatisfactory."

US Defense Secretary Jim Mattis responded in a television interview on Sunday, assuring that Trump was "wide open on this issue as he takes in the pros and cons of that accord".

Cohn, the Trump economic adviser, also said last week that the president’s views were "evolving".

UN Secretary General Antonio Guterres has weighed in, arguing on Tuesday that the United States should not leave the Paris Agreement.

"But even if the government decides to leave the Paris agreement, it’s very important for US society as a whole -- the cities, the states, the companies, the businesses -- to remain engaged," he said. — AFP