President Trump will pull the United States out of the Paris climate change agreement, according to several reports Wednesday.

Axios first reported that Trump is working with a group led by Environmental Protection Agency Administrator Scott Pruitt on the exact mechanism of pulling out before announcing his final decision. CBS News also reported that Trump is telling allies about his decision.

The move marks a dramatic departure from the Obama administration, which was instrumental in crafting the deal. It also makes the U.S. an outlier among the world's nations, nearly all of whom support the climate change accord.

But Trump's decision fulfills an original campaign promise he made just more than a year ago to "cancel" the accord.

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

A White House spokeswoman refused to confirm or deny that a final decision has been made. She said an announcement would be coming in the next few days and that staff did not want to get ahead of the president's decision.

Trump had been telling close confidants about his decision in recent weeks, Axios reported. But a public letter sent to him last week by 22 Senate Republicans, led by Majority Leader Mitch McConnell (R-Ky.), helped seal his decision.

The agreement was reached by nearly 200 countries in 2015, the first global climate accord to include that many nations. Each country made its own nonbinding pledges to cut greenhouse gas emissions.

The Obama administration, which helped negotiate the pact, had promised a 26 to 28 percent cut in the country's emissions, a pledge that Republicans had slammed as necessitating expensive, job-killing regulations.

Trump, who doubts the science behind climate change, has already begun the process of reversing American climate policies.

In March, he signed an executive order to undo most of Obama's climate agenda, including a key rule to cut electricity sector carbon emissions, and he has proposed gutting funding to federal agencies that tackle climate change, renewable energy and the environment.

He delayed a decision on the Paris deal until after last week's Group of Seven summit in Italy, where foreign leaders pressured him to stay in the agreement.

The White House said Trump was considering the leaders' opinions on the agreement, but others, led by German Chancellor Angela Merkel, characterized the summit more as a six-on-one debate over the merits of the deal, with Trump standing alone.

His decision to leave the deal comes after scores of stakeholders asked Trump to keep the U.S. in the agreement, including businesses, environmentalists, major energy companies, Democrats, a handful of congressional Republicans and some officials in his administration.

Numerous companies and individuals aligned with Trump on other policies have publicly pushed him recently to remain in the agreement, including ExxonMobil Corp. and Cloud Peak Energy. They argued the U.S. needs to stay involved in climate work to have influence over global policy decisions that could impact their bottom lines.

Several GOP lawmakers, such as Sens. Lindsey Graham (S.C.) and John McCain (Ariz.), had hoped he would stay in the deal as well.

But the president was also facing significant pressure from the right to exit the pact, including from Pruitt, White House strategist Stephen Bannon and major conservative groups like the Competitive Enterprise Institute and Heritage Foundation, as well as the 22 GOP senators who sent him the letter last week.

Within the White House, coalitions rose up in support of, or opposed to, the Paris deal. Pruitt and Bannon led the charge against the deal, while Secretary of State Rex Tillerson, top advisers Gary Cohn and Jared Kushner and first daughter Ivanka Trump, who is married to Kushner, supported staying in the accord.

Under Trump's decision, the U.S. will stand with only two nations in not participating in the Paris agreement: Syria and Nicaragua. All other 194 countries in the United Nations' Framework Convention on Climate Change have signed on, and 146 have ratified the agreement.

It is unclear whether Trump will work through the four-year exit process within the agreement or declare that since it is not binding, he can bypass it.

Updated at 9:21 a.m.