Critics of the Paris climate change deal stepped up their offensive Wednesday to pressure President Trump to keep his campaign promise and withdraw from the international pact on global warming.

The free-market Competitive Enterprise Institute think tank in Washington is leading the charge to ensure Trump leaves the deal, releasing an exhaustive analysis on why staying in the deal would harm the U.S. economy.

The cost of meeting the climate change agreement will dwarf that of meeting just the climate regulations established under former President Barack Obama's climate change plan. Obama's regulations make up the U.S.'s preliminary commitment toward meeting the goals of the Paris deal. But as the agreement progresseses new, much more strict rules will be required, with added costs.

"Obama pledged to reduce U.S. emissions by 26 to 28 percent below 2005 levels by 2025, with deeper cuts every five years thereafter. That is already significant, but he went much further," the report said. "He also committed the United States to rapidly phase out fossil fuels over 35 years."

The cost risk would rise through 2050, as the deal would require an increase in the U.S.'s commitments every five years. "Just the first U.S. ... emission reduction pledge ... outstrips the achievable emission reductions of all adopted and proposed Obama climate policies, including the Clean Power Plan and other regulations Trump is rescinding, by about 49 percent," it read.

The Clean Power Plan has been estimated to cost the U.S. economy $39 billion each year if implemented. An often-cited report by NERA Economic Consulting showed that the cost of meeting the plan could total as much as $300 billion between 2022 to 2033.

On top of that, new legislation would be required to meet the initial commitment and future "more ambitious" commitments under the agreement, the CEI report said, including a $10-per-barrel carbon fee on oil that Obama proposed in his fiscal 2017 budget.

"In addition, the agreement falls apart unless Congress ponies up billions for the Green Climate Fund," it added. The fund is meant to be authorized at $100 billion per year by 2020, but countries want that amount to be increased. The money would be used to assist smaller countries to cope with the effects of global warming such as sea-level rise.

The study comes as new reports suggested Trump is leaning toward withdrawing from the agreement, after finding out that the U.S.'s commitments under the deal would be impossible to reverse.

Trump senior adviser and son-in-law Jared Kushner and Secretary of State Rex Tillerson have been arguing for the U.S. not to leave the agreement, which is non-binding.

Republican strategist Mike McKenna told the Washington Examiner that he thinks Tillerson's influence has been fading in recent weeks. "I think he is going to exit," he said in an email. He added that "the State Department is on a pretty lonely island right now."

The new CEI study said the State Department's suggestions on how to remain a party to the agreement, without abiding by the commitments made under former President Barack Obama, present a "false choice."

"The argument that we can simply renegotiate the Paris Climate Treaty is false; that's not an option under the deal," said Chris Horner, co-author of the study and senior fellow at CEI. "The agreement's language in Article 4 is clear and deliberate. According to this treaty, any revision must be more stringent — we cannot revise downward, and we are required to make it worse, every five years, forever. This is a truly terrible deal for U.S. consumers and the economy."

CEI argues that the climate agreement acts as a treaty, even though it's non-binding, because it has real domestic consequences for the nation's energy policy that can be upheld by federal courts.

Horner said remaining a party to the deal gives Democratic state attorneys general, environmental groups and other supporters room to maneuver in the courts to use Paris to uphold strict climate regulations. Those regulations would have real economic impact on the nation's economy, according to CEI.

Myron Ebell, CEI's environmental program director, has been leading the group's campaign to pressure Trump to leave the Paris agreement. Ebell is the former head of the Trump transition team for the Environmental Protection Agency.

"We are hopeful that President Trump will keep his campaign promise to withdraw from the Paris Climate Treaty, but we aren't taking that for granted," Ebell said in an email.

The think tank has released two online ads in the last two weeks to get citizens to sign a petition urging Trump to exit from the deal. He said hundreds of thousands have watched the ads, and thousands have signed the petition in the wake of the ad campaign.

CEI and the free-market group Institute for Energy Research are circulating a joint letter among other like-minded nonprofit groups that will be sent to Trump next week, Ebell said.

"And we are talking it up in blogs, op-eds, to reporters ... on TV and radio, and at meetings on the Hill and among the conservative coalition," he said in an email.

Trump is expected to make a decision as soon as next week on whetherto leave the Paris agreement.

The New York Times and Huffington Post reported late Tuesday that the White House is now leaning toward exiting from the deal as the only course left to consider. Trump said last week that he will make a decision on the deal in two weeks.