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President Donald Trump is leaning toward pulling the United States out of the global deal to cut greenhouse gas emissions, two administration sources told NBC News on Wednesday — part of the landmark 2015 accord that nearly every nation in the world signed on to.

Though no final decision has been made, Trump mulling whether to snub the climate agreement — inked in Paris during a United Nations Climate Change Conference — is unsurprising, one source added. During his presidential campaign, Trump threatened to cancel America's involvement and said at a rally a year ago he opposes "draconian climate rules."

Both President Barack Obama and former Vice President Al Gore championed the pact of almost 200 nations.

Trump's potential decision was first reported by Axios, which said details are being worked out by a small team at the White House, including EPA Administrator Scott Pruitt — who has questioned the origins of climate change in the past and in March said he doubts carbon dioxide primarily contributes to global warming.

Related: Big Business Urges Trump to Stick With Paris Climate Accord

Trump tweeted Wednesday that he "will be announcing my decision on the Paris Accord over the next few days."

I will be announcing my decision on the Paris Accord over the next few days. MAKE AMERICA GREAT AGAIN! — Donald J. Trump (@realDonaldTrump) May 31, 2017

A few hours later he tweeted that he will make the announcement at 3 p.m. (presumably ET) on Thursday.

I will be announcing my decision on Paris Accord, Thursday at 3:00 P.M. The White House Rose Garden. MAKE AMERICA GREAT AGAIN! — Donald J. Trump (@realDonaldTrump) June 1, 2017

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During a brief photo opportunity later Wednesday with Vietnamese Prime Minister Nguyen Xuan Phuc, Trump told reporters in the Oval Office that he would make a decision on the Paris accord "very soon."

"I'm hearing from a lot of people, both ways," he said about the climate deal.

The non-binding agreement is set to take effect in 2020, and asks that all signing countries — rich and poor — take concrete steps to reduce their carbon emissions in the face of climate change, while leaving some flexibility for how they do it.

The Obama administration pledged a 26 to 28 percent cut in U.S. emissions, which Republicans have criticized for potentially having a negative impact on the American economy and its energy sector.

Trump has previously called global warming a hoax and during the presidential race warned he would defund any United Nations programs related to climate change. He made good on his promise in his budget proposal released earlier this year, seeking to eliminate a program created by the Obama administration called the Global Climate Change Initiative.

In recent months, both Democrats and some House Republicans have pressed Trump not to exit the deal, acknowledging that scientists overwhelmingly say that climate change is being fueled by man-made greenhouse gas emissions.

Related: Trump Pledges to Rip Up Paris Climate Agreement in Energy Speech

"It is imperative that we maintain our seat at the table in global discussions of how to address the threats posed by climate change," a group of bipartisan lawmakers wrote to the White House in April.

Major companies, including Exxon Mobil, have also urged Trump not to forgo the agreement and allow the U.S. to help set the agenda with the rest of the world. Former Exxon Mobil CEO and now-Secretary of State Rex Tillerson has been more open to addressing climate change and its consequences, and met Wednesday with Trump.

Should the U.S. officially withdraw from the agreement, it would be one of three nonparticipating nations that currently includes Syria, which has been mired in civil war, and Nicaragua, which rejected the pact because it believes the deal doesn't have enough teeth.

Democrats, in particular, decried the possibility of Trump dismantling the Obama administration's environmental legacy.

House Minority Leader Nancy Pelosi tweeted her disappointment, calling the potential move a "stunning abdication of American leadership and a grave threat to our planet's future."

.@POTUS' decision to support a dirty energy agenda & pull out of #ParisAgreement is a grave threat to our planet. https://t.co/qMgx15EDlV — Nancy Pelosi (@NancyPelosi) May 31, 2017

Sen. Al Franken, D-Minnesota, a member of the Senate Energy and Natural Resources Committee, said on MSNBC that U.S. leadership is "disastrous" on the issue and that "climate scientists, the peer-reviewed climate scientists, all say (climate change) is happening."

Organizing for Action, the political group that grew out of Obama's first presidential campaign, said leaving the deal would be a "small-minded decision" on Trump's part.

"Once again, this administration, with support from their rubber stamps in Congress, would be acting against both the will of the American people and the good of the country," OFA spokesman Jesse Lehrich said in a statement.

Tesla CEO Elon Musk, a member of the White House's business advisory council, tweeted that he has advised Trump personally about remaining in the Paris accord. He also warned that he will "have no choice" but to personally give up his role if the president responds differently.

Don't know which way Paris will go, but I've done all I can to advise directly to POTUS, through others in WH & via councils, that we remain — Elon Musk (@elonmusk) May 31, 2017

Will have no choice but to depart councils in that case — Elon Musk (@elonmusk) May 31, 2017

And European Commission President Jean-Claude Juncker mocked Trump on Wednesday, saying:

"That's not how it works. The Americans can't just leave the climate protection agreement. Mr. Trump believes that because he doesn't get close enough to the dossiers to fully understand them. It would take three to four years after the agreement came into force in November 2016 to leave the agreement. So this notion 'I am Trump, I am American, America First and I'm going to get out of it,' that won't happen. We tried to explain that to Mr. Trump in Taormina in clear German sentences. It seems our attempt failed."