President Trump is expected to announce Thursday that his administration will back out of the Paris Climate Agreement that was agreed upon in 2015 by nearly 200 countries, including the Obama administration, two sources told Fox News.

Trump, who vowed to pull out of the deal during the 2016 campaign, is expected to withdraw, but officials cautioned that there may be "caveats in the language,” leaving open the possibility that the decision is not final, a senior White House source told The Associated Press.

The accord would have forced the U.S. to reduce fossil fuel emissions by nearly 30 percent by 2025.

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

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

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 U.N. climate change treaty on which the accord was based.

Top House Democrat Nancy Pelosi said in a statement that the decision to pullout would be a "stunning abdication of American leadership and a grave threat to our planet's future."

Ryan Zinkie, Trump’s Interior Secretary, told reporters at a news conference in Anchorage Wednesday that he can’t comment on the agreement because he hasn’t read up on it.

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

In a possible jab at the likely U.S. pullout, the United Nations tweeted on Wednesday a quote from Secretary General Antonio Guterres: "Climate change is undeniable. Climate action is unstoppable. Climate solutions provide opportunities that are unmatchable."

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 canceling construction of about 100 coal-fired power plants and investing billions in massive wind and solar projects.

Fox News’ John Roberts and The Associated Press contributed to this report.