US President Donald Trump, who has repeatedly expressed readiness to withdraw from the deal during his presidential election campaign, wrote on Twitter that he would announce his decision on participation in the global agreement, at 3 p.m. local time (19:00 GMT) on Thursday.
Economists say a US pullout could give American exports an unfair price advantage compared to products from the European Union, where industries must pay penalties for emitting carbon dioxide. The president has pledged to reverse decades of decline in coal mining, which now accounts for fewer than 75,000 U.S.jobs.
Though it remains the largest global carbon emitter, China also leads the world in total installed solar and wind capacity. Former President Barack Obama had agreed to reduce the country's emissions to 26 percent to 28 percent of 2005 levels by 2025 - about 1.6 billion tons.
Reports of the impending move by the American president triggered statements of support for the climate accord from scores of world leaders.
EU Commissioner for Energy and Climate Action Miguel Arias Canete said the world could count on European climate leadership. Top White House aides have been divided, and Trump's decision may not be entirely clear-cut.
Juncker said the Group of Seven leaders "tried to explain in clear simple sentences to Trump" at a recent summit in Italy.
The agreement itself, negotiated in late December 2015 and championed by the Obama administration, presents a rare case of near-total global unanimity.
What is not yet clear is whether Trump plans to initiate a formal withdrawal from the Paris accord, which under the terms of the agreement could take three years, or exit the underlying United Nations climate change treaty on which the accord was based.
A US departure could have sweeping implications.
But Obama says he's confident nonetheless that US cities, states and businesses will fill the void by taking the lead on protecting the climate. The former reality TV star with a flair for drama later promoted his Rose Garden announcement in a tweet. Trump is largely expected to pull out, which could have a devastating effect on the worldwide plan to reduce pollution.More news: Theresa May slammed for no-show in noisy and ill-tempered debate
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The president has previously called climate change a "hoax", tweeting in 2012, "The concept of global warming was created by and for the Chinese in order to make USA manufacturing non-competitive".
Abandoning the pact was one of Trump's principal campaign pledges.
That's according to multiple congressional officials and others briefed by the White House on the decision.
"The US is already leading the world in energy production and doesn't need a bad deal that will harm American workers", it read.
A source close to the matter said Trump was preparing to pull out of the agreement.
French President Emmanuel Macron, German Chancellor Angela Merkel and Italian Premier Paolo Gentiloni said in a joint statement Thursday that they take note "with regret" the US decision to pull out of the 2015 agreement.
"We're getting out", he said.
"It goes without saying that the effectiveness of this convention is likely to be reduced without its key participants", a Kremlin spokesman said. "President Putin signed this convention in Paris", Kremlin spokesperson Dmitry Peskov told a conference call with reporters on Thursday.