WASHINGTON — President Trump announced Thursday that he will withdraw the United States from participation in the Paris climate accord, weakening global efforts to combat climate change and siding with conservatives who argued that the landmark 2015 agreement was harming the economy.
But he will stick to the withdrawal process laid out in the Paris agreement, which President Barack Obama joined and most of the world has already ratified. That could take nearly four years to complete, meaning a final decision would be up to the American voters in the next presidential election.
Still, Mr. Trump’s decision is a remarkable rebuke to fellow heads-of-state, climate activists, corporate executives and members of the president’s own staff, all of whom failed this week to change Mr. Trump’s mind with an intense, last-minute lobbying blitz.
It makes good on a campaign promise to “cancel” an agreement he repeatedly mocked and derided at rallies, saying it would kill American jobs. As president, he has moved rapidly to reverse Obama-era policies designed to allow the United States to meet its pollution-reduction targets as set under the agreement.
“In order to fulfill my solemn duty to protect America and its citizens, the United States will withdraw from the Paris climate accord but begin negotiations to re-enter either the Paris accord or an entirely new transaction on terms that are fair to the United States,” the president said. “We are getting out. But we will start to negotiate, and we will see if we can make a deal that’s fair. And if we can, that’s great.”
Mr. Trump said that the United States will immediately “cease all implementation of the nonbinding Paris accord” and what he said were “draconian financial” and other burdens imposed on the country by the accord.
In his remarks, Mr. Trump listed sectors of the United States economy that would suffer lost revenues and jobs if the country remained part of the accord, citing a study — disputed vigorously by environmental groups — that claims the agreement would cost 2.7 million jobs by 2025.
Mr. Obama, in a rare assertion of his political views as a former president, castigated the decision.
“The nations that remain in the Paris Agreement will be the nations that reap the benefits in jobs and industries created,” he said in a statement. “I believe the United States of America should be at the front of the pack. But even in the absence of American leadership; even as this Administration joins a small handful of nations that reject the future; I’m confident that our states, cities, and businesses will step up and do even more to lead the way, and help protect for future generations the one planet we’ve got.”
Most Republicans applauded the decision.
“I applaud President Trump and his administration for dealing yet another significant blow to the Obama administration’s assault on domestic energy production and jobs,” said Senator Mitch McConnell of Kentucky, the majority leader.
Senator John Barrasso of Wyoming, chairman of the Senate Committee on Environment and Public Works, said, “The Paris climate agreement set unworkable targets that put America at a competitive disadvantage with other countries and would have raised energy costs for working families.”
But Senator Susan Collins, Republican of Maine, tweeted, “Climate change requires a global approach. I’m disappointed in the President’s decision.”
In recent days, Mr. Trump withstood withering criticism from European counterparts who accused him of shirking America’s role as a global leader and America’s responsibility as the world’s second largest emitter of planet-warming greenhouse gasses. And he shrugged aside pleas from executives of the United States’ largest companies, who said the decision will damage the environment and hamper their efforts to compete around the world.
Mr. Trump also found himself at the center of a bruising, monthslong debate inside the White House that pitted senior members of his staff against each other. Some argued to leave the Paris agreement and others insisted that the United States should remain, even as the administration dismantles pollution standards.
The president’s decision was a victory for Stephen K. Bannon, his chief strategist, and Scott Pruitt, his Environmental Protection Agency administrator, both of whom had argued forcefully to abandon the global agreement in favor of a clean break that would clear the way for a new environmental approach.
Other top aides, including Gary D. Cohn, the director of the National Economic Council; the president’s daughter, Ivanka Trump; and his secretary of state, Rex W. Tillerson, had insisted to Mr. Trump that remaining a part of the agreement would have allowed the United States to eviscerate Obama-era climate rules without as much damage to relations with other countries.
After the fierce debate of the past weeks, the White House took on the trappings of a celebration. The Rose Garden was packed with reporters, activists and members of Mr. Trump’s administration, who waited in at the hot sun for the president’s announcement. Scores of staff members lined the sides of the Rose Garden as a military band played soft jazz.
Supporters of the Paris agreements reacted with pent-up alarm, condemning the administration for shortsightedness about the planet and a reckless willingness to shatter longstanding diplomatic relationships.
“This is disgraceful,” said Annie Leonard, Greenpeace USA’s executive director. “By withdrawing from the Paris Climate Agreement, the Trump administration has turned America from a global climate leader into a global climate deadbeat.”
Kierán Suckling, executive director of the Center for Biological Diversity, said, “Trump just confirmed his total contempt for our planet’s future,” condemning “this reckless rejection of international climate cooperation” that was “turning our country into a rogue nation.”
Corporate leaders also condemned Mr. Trump’s action. In a statement on its website, I.B.M. reaffirmed its support for the Paris agreement and took issue with the president’s contention that it is a bad deal for American workers and the American economy.
“This agreement requires all participating countries to put forward their best efforts on climate change as determined by each country,” the company said in the statement. “IBM believes that it is easier to lead outcomes by being at the table, as a participant in the agreement, rather than from outside it.”
Jeff Immelt, chairman and chief executive of General Electric, took to Twitter to say he was “disappointed with today’s decision on the Paris Agreement. Climate change is real. Industry must now lead and not depend on government.”
But Mr. Trump was resolute.
“It is time to put Youngstown, Ohio, Detroit, Mich., and Pittsburgh, Pa., along with many, many other locations within our great country before Paris, France,” he said. “It is time to make America great again.”
Pittsburgh Mayor Bill Peduto responded on Twitter, “I can assure you that we will follow the guidelines of the Paris Agreement for our people, our economy & future.”