Nearly 200 countries agreed to the 2016 pact that would curb climate-changing climate emissions. The US would become only the third country to reject the accord -- joining a club that includes just two other members: Syria and Nicaragua.
Trump campaigned hard against the Paris agreement, and has called climate change a "hoax" perpetrated by the Chinese to gain economic advantage over the US.
After winning the election, he appointed as administrator of the Environmental Protection Agency Scott Pruitt, an Oklahoma lawyer who made a name for himself fighting the EPA's efforts on climate change and clean air, often working closely with the fossil fuel industry to do so.
Nicaraguan and Syrian representatives in the US didn't respond to CNN's requests for comment about their decisions not to become party to the Paris agreement. If the US joins them in opposing the deal, it would make for an odd alignment -- and could be bad for US optics around the globe. Syria, of course, is waging a war against its own citizens that has raised concerns about possible crimes against humanity.
While Nicaragua raises no such issues, the Latin American country and Syria do share a significant difference with the US when it comes to greenhouse gases: scale. A decision to pull out of the pact will make the US the world's largest carbon emitter outside the Paris agreement.
Trump, asked Wednesday afternoon if he had made a decision on whether to exit the Paris climate accord, responded, "Very soon."
"I'm hearing from a lot of people, both ways. Both ways," he told reporters at the White House.
"Better being at the table than leaving"
The voluntary agreement has countries work to limit global temperature increases during this century to within two degrees Celsius above pre-industrial levels and try to limit the rise even further to 1.5 degrees Celsius.
Trump's cabinet officials, including Secretary of State Rex Tillerson and Defense Secretary James Mattis, have said that they believe in climate change. Tillerson -- a former ExxonMobil CEO -- signed an international declaration
in April acknowledging the threat climate change poses to the Arctic. And during his confirmation hearing, he told senators that "I think we're better served by being at the table than leaving that table." The Pentagon takes it into account in its military planning.
Conservative critics have praised the President's stance. Brett Schaefer, a senior research fellow at the Heritage Foundation, said, "the Paris agreement is a costly and ineffective approach to global warming, and both the diplomatic costs of leaving and the benefits of staying have been exaggerated."
But others in the conservative camp think abandoning the pact is a mistake.
"I would stay in the agreement and make it a better deal for worldwide business interests, to improve the climate, better deal for business," Sen. Lindsey Graham, a South Carolina Republican, told CNN's Dana Bash. "If he does withdraw, that would be a definitive statement by the President that he believes climate change is a hoax. Stay in the deal, make it a better deal, would be my advice."
The Pope weighs in
Throughout, Trump has continued to telegraph his ambivalence, refusing to commit one way or another during his first overseas trip this month. Throughout, the issue of climate hovered. Pope Francis gave Trump a pointed gift -- his encyclical "Laudato Si," which calls for science and religion to partner in a drive to fight human causes of climate change.
Climate came up later in the trip at the G-7 meeting where the leaders of Japan, Germany, France, Britain, Italy and Canada reaffirmed their commitment to the deal.
Trump tweeted afterward that "I will make my final decision on the Paris Accord next week!" At the meeting, CNN reported that Trump told French President Emmanuel Macron he was under pressure to back out. "A lot of people in my country are against this agreement," Trump said.
In reality, 69% of Americans support the Paris agreement, seven in 10 Americans say global warming is happening and more than half think it's being caused by humans, according to a January poll
by the Yale Program on Climate Change Communication and the George Mason University Center for Climate Change Communication.
European leaders telegraphed their expectation that Trump would not stick with the US commitment to the deal.
"The entire discussion about climate was very difficult, if not to say very dissatisfying," German Chancellor Angela Merkel said at a press conference after the G-7. "There are no indications whether the United States will stay in the Paris agreement or not."
Derek Chollet, a former defense department official in the Obama administration, said Trump's likely withdrawal from the Paris agreement marks a dark irony.
"The irony is that in the first few years of the Obama administration, we had to spend a lot of time with the Chinese convincing them our climate change agenda wasn't a Trojan Horse to limit their economic growth," Chollet said. "We successfully worked them to the point -- and reality set in -- that they found religion and now positions have reversed. Now they're leading the charge on climate change."