The White House has continued to delay a decision on whether it will stay in the Paris climate agreement, but pressure is mounting on the president from both Republicans and Democrats to keep the U.S. in the deal, albeit for different reasons.

Democrats, like environmental groups, see the accord as crucial in efforts to slow global warming. And while many Republicans despise the deal, they fear leaving it would undermine U.S. global leadership and take away the opportunity to reshape, even weaken the accord.

At a Wednesday news conference and in a letter to President Donald Trump, Senate Democrats led by Minority Leader Charles E. Schumer warned that leaving the deal would be a “historic mistake” and turn the U.S. into an “international pariah.”

Under the deal spearheaded by former President Barack Obama, the U.S. agreed to reduce its carbon emissions by 26-28 percent from 2005 levels by 2025. The agreement also requires nations to report on their progress and submit new, more ambitious targets every five years starting in 2020.

“All of that would be undone in one fell swoop,” Schumer said.

The Democrats also said that moving away from the agreement would allow other countries like China to take the “moral high ground.”

“Countries like Russia and China know that if the U.S. leaves, there is going to be opportunity for them,” Senate Foreign Relations Committee ranking member Benjamin L. Cardin, D-Md., said.

During a presidential visit to the Vatican on Wednesday, Pope Francis gave Trump a copy of his writings on climate change and the Vatican Secretary of State Cardinal Pietro Parolin urged the president to step up climate change efforts and stay in the accord.

“The president indicated we’re still thinking about that . . . that he hasn’t made a final decision,” Secretary of State Rex Tillerson told reporters of the Vatican’s urging the U.S. to stay in the agreement, according to White House press pool reports . “We’re developing our own recommendation on that. So it’ll be something that will probably be decided after we get home.”

Campaign promise

During the presidential campaign, Trump continually criticized the agreement as a bad deal and vowed to walk away from it on his first day in office. But four months later, no decision has been made and the White House’s position has become increasingly unclear as Trump and his advisers debate what direction to take. The White House has twice called off plans to announce its position on the agreement. Trump is expected to make a decision after the G7 summit, which ends on Sunday.

In April, Rep. Kevin Cramer , R-N.D., who helped shape Trump’s energy policy positions during the campaign, led a letter of nine GOP House members advocating that the U.S. renegotiate the global agreement ’s goals for reducing climate-altering emissions from fossil fuels like coal and oil.

The letter said that the U.S. should use its position in the agreement to “defend and promote” the country’s commercial interests including manufacturing and the fossil fuel industry.

“Our engagement must prevent the development of harmful policies which undermine economic growth and energy security here and abroad,” said the Republican letter, which was also signed by Reps. Larry Bucshon of Indiana, Earl L. “Buddy” Carter of Georgia, Chris Collins of New York, Virginia Foxx of North Carolina, Gregg Harper of Mississippi, Mike Kelly of Pennsylvania, Billy Long of Missouri and Markwayne Mullin of Oklahoma.

Industry advocates, including fossil fuel companies like Exxon Mobil Corp. and Cloud Peak Energy Inc. and Shell Oil Co., have also encouraged the White House to remain in the deal. But key administration officials like EPA Administrator Scott Pruitt and White House adviser Steven Bannon have pushed for a quick U.S. exit.

In Congress, influential Republicans, including Senate Environment and Public Works Chairman John Barrasso of Wyoming and his predecessor and senior committee member James M. Inhofe of Oklahoma remain adamantly opposed to the agreement.

“Many of America’s global competitors are unaffected by the Paris agreement, while the United States will incur significant implementation costs,” the Senate Republican Policy Committee, headed by Barrasso, said in an April memo, warning that “every sector of the economy will be affected, especially the U.S. industrial base.”