Trump likely to withdraw US from Paris climate accord, senior WH official says Trump had delayed a decision.

 -- President Trump is likely to withdraw the United States from the Paris climate accord, a move that would fulfill a key campaign promise and upend a signature achievement of his predecessor, administration officials told ABC News.

Although the officials caution no decision is final until the president officially announces it, the White House is now working on how to roll out the announcement and explain the reasons behind Trump's decision.

Trump tweeted Wednesday night that he will announce his decision on Thursday at 3 p.m.

The president is also facing intense eleventh-hour lobbying from both inside and outside the administration to keep the United States as part of the accord. At the center of it: Gary Cohn, the president’s chief economic adviser – and a Democrat - who supports staying in.

White House sources characterize Trump as about 95 percent decided on pulling out of the deal, and one source says the motivation behind today’s leak to Axios, which first reported the president was definitely backing out of the Paris accord, may be to force the president into making a decision on this once and for all.

On Twitter, Trump teased the announcement of his decision as imminent this week.

If Trump decides to withdraw the United States from the global climate accord, it would be seen as a win for chief strategist Steve Bannon and those aligned with him who have urged the president to pull out of the landmark agreement. But it would also be seen as a loss for Trump’s daughter Ivanka Trump and son-in-law Jared Kushner, who reportedly back in February pushed the president to remove language critical of the Paris accord from an executive order related to environmental issues.

Though he regularly criticized the climate deal on the campaign trail, Trump has been mulling a decision on whether to withdraw or remain in the Paris climate deal for some time.

The uncertain future of U.S. involvement in the accord pushed even big oil companies like Shell and Exxon, as well as tech companies large and small, to make an appeal to the Trump administration not to back out of the agreement. On the other hand, 22 GOP senators, including Senate Majority Leader Mitch McConnell of Kentucky, penned a letter to the White House arguing that the United States should pull out of the Paris accord because it would reduce legal challenges to efforts to roll back other environmental regulations.

Before being sworn into office, Trump told The New York Times in a November interview that he was looking at the climate accord "very closely" and that he has "an open mind to it.”

But he so far has taken steps to roll back other Obama-era climate policies, like the Clean Power Plan, and put Scott Pruitt, who has slammed the accord as a "bad deal," in charge of the Environmental Protection Agency.

During Trump's foreign trip that included a stop at the Vatican, Pope Francis gave Trump a copy of his encyclical on climate change and, according to Secretary of State Rex Tillerson, the cardinal secretary of state "encourag[ed] continued participation in the Paris accord."

“If President Trump reads the Pope's writings, I'm confident he will not withdraw from the agreement. We got to get him to read it,” Senate Minority Leader Chuck Schumer, D-N.Y., said during a news conference on Capitol Hill last week announcing that he and 39 other Democratic senators sent a letter to Trump, demanding the United States remains a party to the Paris agreement.

The issue of climate change and the U.S. stance in the Paris climate accord was also pushed on Trump during the G-7 summit in Sicily last week.

“He came here to learn,” Trump chief economic adviser Gary Cohn said at the G-7 summit Friday. “So his views are evolving, which is exactly what they should be.”

If the United States were to pull out of the accord, it would join Syria and Nicaragua as three out of the 145 countries that have signed on to the 2015 agreement sponsored by the United Nations to slow climate change.

When asked Tuesday whether the president thinks human activity contributes to climate change, press secretary Sean Spicer said, "Honestly, I haven't asked him."