If President Donald Trump is going to pull the United States out of the Paris climate agreement, he should get out of the way now and let the rest of the world work toward a solution, says William K. Reilly, who headed the Environmental Protection Agency when the world's first global treaty on climate change was forged in 1992.

Reilly, who considers Trump's decision a "tragedy," said one of his greatest fears is that the administration will continue to meddle in the international negotiations as other countries try to implement and strengthen the Paris accord.

"One hopes that this is it for the United States in terms of trying to do damage to the agreement," Reilly said on this week's Columbia Energy Exchange podcast, produced by Columbia University's Center on Global Energy Policy. In an interview with center director Jason Bordoff, a former climate advisor to President Barack Obama, Reilly said, "There's a possibility of the United States playing a role to try to reduce the commitments or aspirations that are agreed to in future. ... And that would be very unfortunate and pernicious."

In line with Trump's stated desire to "have the United States go it alone," Reilly said, it would be better for his State Department to skip the upcoming meetings of the treaty parties, the next of which is scheduled for Bonn, Germany, in November. "I hope that he will not send people to those delegations," Reilly said.

But a State Department official said that the U.S. will remain engaged in the climate talks.

"We want to work with our allies and partners to seek common ground and develop a way forward on this important issue," the official said, noting Secretary of State Rex Tillerson's remarks on the importance of continued involvement. "The United States needs a balanced approach to climate policy—one that promotes American jobs, economic prosperity, and energy security," the official said.

Longtime close observers of international climate negotiations said that they could not imagine the United States opting to disappear from the talks.

Even when President George W. Bush exited the Kyoto treaty in 2001, his State Department continued to participate in climate negotiations. Under the Paris rules, the U.S. will not be able to withdraw officially for about four years, and Trump maintained U.S. participation in the overarching treaty—the United Nations Framework Convention on Climate Change.

Among those who hope for further international progress on climate change, opinion is mixed on whether Reilly's fears are founded.

Alden Meyer, director of strategy and policy for the Union of Concerned Scientists, said he does not believe that the U.S. would publicly try to intervene to block or derail the continuing negotiations to implement the Paris accord. "The other countries would call them out on that and say that is unacceptable," said Meyer, who has more than 30 years of experience as an observer at international environmental talks.

But behind the scenes, in trade negotiations or in meetings like the G-7 meeting of environment ministers in Italy this week (attended by EPA Administrator Scott Pruitt), Meyer said he is concerned that the United States could put pressure on other countries to stymie climate progress. That kind of behind-the-scenes pressure was evident in a leaked draft of the Arctic Council's declaration earlier this year in which the administration tried to remove or weaken several climate change references.

"Given the stance the administration has taken, and their desire to ramp up fossil fuel use," Meyer said, "I think you have to be very alert to their activities and motivations. I am concerned they will use their economic and diplomatic might to try to slow down the process of decarbonization of the global economy."

Susan Biniaz, a former State Department official who worked on climate negotiations in both Republican and Democratic administrations, said that she thinks that continued engagement by the Trump administration could be positive—especially given the fact that Trump left open the possibility of reentering the agreement on changed terms in the future.

"To the extent that they are able to come up with guidelines and rules that make it more likely that they stay in the regime, the better," said Biniaz, who is now a senior fellow at the nonprofit UN Foundation.

Biniaz argued that when President George W. Bush's administration stayed engaged in climate talks even after exiting the Kyoto protocol, it helped lay the groundwork for the eventual Paris accord. "You can draw a line from the objections made by the Bush administration directly to the agreement that was reached at Paris," she said.

"What is kind of baffling to all of us is that the objections to Kyoto—that major developing countries were excluded, that there was no flexibility—every one of those was fixed in Paris," Biniaz added.

Reilly, a former president of the World Wildlife Federation, is one of the most prominent members of a past and all-but-lost generation of Republican environmental leaders. His bipartisan cachet is such that he was appointed by Obama as co-chair of the National Commission on the BP Deepwater Horizon Oil Spill.

Reilly played a pivotal role in the 1992 Earth Summit in Rio, helping steer it toward the UNFCCC treaty, which sought to address not only environmental issues, but economic development, on behalf of President George H.W. Bush. "American environmental policy is not going to be dominated by the extremes," Bush said at the time.

Now Reilly, assessing the course that a Republican administration is setting for the nation 25 years later, thinks it would be better for the United States to stand back from the treaty he helped shape.

"It would indicate bad faith, I think, if we're just there basically to sabotage the efforts of the other countries, which is now all that's left if the United States is not involved," Reilly said. "I hope, in sum, that it's a clean walk-away on the part of the president if that's the decision that has been made."