If Trump pulls out of climate deal, US could join Syria and Nicaragua as nonparticipants

— -- If President Trump decides to pull out of the 2015 Paris accord on climate change, the United States could become one of only three nations in a U.N. climate group not to be signed onto the deal.

Trump announced in a tweet Saturday that he would make his "final decision" this week on whether or not to keep the U.S. in the landmark accord in which nations agreed to work toward curbing greenhouse gas emissions to address climate change.

"I will make my final decision on the Paris Accord next week!" the president wrote.

The president's tweet came after meetings with other world leaders who pushed for the U.S. to remain in the Paris agreement.

“There is one open question, which is the U.S. position on the Paris climate accords," Italian Prime Minister Paolo Gentiloni said at the Group of Seven summit in Italy on Friday. "All others have confirmed their total agreement on the accord.”

Trump was also asked by Pope Francis at the Vatican last week to keep the U.S. in the climate change accord.

The December 2015 deal has as of this month been signed by all 197 countries in the United Nations Framework Convention on Climate Change except two: Syria and Nicaragua. Of the 195 that have signed, 147 have ratified the accord.

If the U.S. pulls out of the Paris deal, it would become the largest producer of greenhouse gas emissions not included in the agreement, according to EPA data.

Trump has at times seemed to downplay concerns over climate change.

As a candidate on Dec. 1, 2015, Trump posted a video on Instagram -- while the 2015 United Nations Climate Change Conference was taking place -- in which he criticized then-President Obama for "worrying about global warming."

"What a ridiculous situation," Trump said in the post.

Trump's chief economic adviser, Gary Cohn, told reporters at the G-7 summit Friday that the president was growing more attuned to the European stance on climate change.

"I think he is learning to understand the European position,” Cohn said when asked which way the president was leaning on the Paris agreement. “Look, as you know from the U.S., there's very strong views on both sides.”

“He came here to learn,” Cohn said at the summit. “So his views are evolving, which is exactly what they should be.”

ABC News' Jordyn Phelps and the Associated Press contributed to this report.