Mr. Trump has repeatedly expressed doubts about climate change, at times calling it a hoax to weaken U.S. industry.

U.S. President Donald Trump is expected to withdraw the United States from the Paris climate accord, a White House official said on Wednesday, confirming a move certain to anger allies that spent years negotiating the landmark agreement to reduce carbon emissions.

But there may be “caveats in the language” that Mr. Trump uses to announce the withdrawal, leaving open the possibility that the decision isn’t final, according to the official, who insisted on anonymity in order to discuss the decision before the official announcement.

Mr. Trump tweeted on Wednesday morning: “I will be announcing my decision on the Paris Accord over the next few days. MAKE AMERICA GREAT AGAIN!”

Nearly 200 nations, including the United States under President Barack Obama’s administration, agreed in 2015 to voluntarily reduce their greenhouse gas emissions in an effort to combat climate change. Withdrawing would leave the United States aligned only with Russia among the world’s industrialised economies in rejecting action to combat climate change.

During Mr. Trump’s overseas trip last week, European leaders pressed him to keep the U.S. in the pact.

Mr. Trump has repeatedly expressed doubts about climate change, at times calling it a hoax to weaken U.S. industry. An overwhelming majority of scientists, however, say climate change is driven by human use of fossil fuels.

Word of Mr. Trump’s decision comes a day after the President met with Scott Pruitt, the administrator of the Environmental Protection Agency. Like his boss, Mr. Pruitt has questioned the consensus of climate scientists that the Earth is warming and that man-made climate emissions are to blame.

Since taking office, Mr. Trump and Mr. Pruitt have moved to delay or roll back federal regulations limiting greenhouse gas emissions while pledging to revive the long-struggling U.S. coal mines.

What is not yet clear is whether Mr. 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 U.N. climate change treaty on which the accord was based.

The U.S. is the world’s second largest emitter of carbon, following only China. Beijing, however, has reaffirmed its commitment to meeting its targets under the Paris accord, recently cancelling construction of about 100 coal-fired power plants and investing billions in massive wind and solar projects.

Mr. Trump had vowed during his campaign to “cancel” the Paris deal within 100 days of becoming President, as part of an effort to bolster U.S. oil and coal industries. That promise helped rally supporters sharing his scepticism of global efforts to police U.S. carbon emissions.

After taking office, however, Mr. Trump faced pressure to stay in the deal from investors, international powers and business leaders, including some in the coal industry. He also had to navigate a split among his advisers on the issue.

Mr. Trump’s aides including Steve Bannon, Stephen Miller, lawyer Don McGahn and Peter Navarro, along with Mr. Pruitt, argued hard for leaving the accord. They said the deal would require the U.S. government to regulate greenhouse gas emissions, which would hurt business.

Mr. Trump’s administration has already begun the process of killing Obama-era climate regulations.

The “stay-in” camp, which included Mr. Trump’s daughter Ivanka, chief economic adviser Gary Cohn, and Energy Secretary Rick Perry, had argued the United States could reduce its voluntary emission-cuts targets while still keeping a voice within the accord.

Oil majors Shell and Exxon Mobil have also supported the Paris pact, along with a number of Republican lawmakers. Several big coal companies, including Cloud Peak Energy, had publicly urged Trump to stay in the deal as a way to help protect the industry’s mining interests overseas, though others asked Trump to exit the accord to help ease regulatory pressures on domestic miners.