"The United States will withdraw from the Paris Climate Accord, but begin negotiations to re-enter either the Paris Accord or really an entirely new transaction on terms that are fair to the United States," the president said in the Rose Garden. "So we are getting out, but we are starting to negotiate and we’ll see if we can make a deal that’s fair."
All implementation of the non-binding portions of the agreement will cease to be enforced by the United States, he said.
The decision fulfills a key promise Trump made on the campaign trail and overturns a major accomplishment by his predecessor, Barack Obama.
Trump's speech in the rose garden centered on what he argued is the negative economic impact of the accord, calling it a bad deal for America.
"The bottom line is that the Paris Accord is very unfair at the highest level to the United States," he said.
Referring to the Paris deal as a "massive redistribution of United States wealth" to other countries, the president made the case that the deal fundamentally disadvantages the U.S. economically, relative to other countries.
"I was elected to represent the citizens of Pittsburgh, not Paris," Trump continued. "I promised I would exit or renegotiate any deal which fails to serve America's interests."
He said the Paris accord would "undermine our economy, hamstring our workers, weaken our sovereignty [and] impose unacceptable legal risk."
Despite the withdrawal, the president noted he would be willing to rejoin the deal under terms that are more favorable to the U.S., or to work on an entirely new agreement.
"I'm willing to immediately work with Democratic leaders to either negotiate our way back into Paris under the terms that are fair to the United States and its workers or to negotiate a new deal that protects our country and its taxpayers," he said.
"It means that that country that’s most responsible for climate change has reneged on its promise to be part of the solution," said Timmons Roberts, a professor of environmental studies at Brown University. "It’s very worrisome that we’re delaying the inevitable work we need to do on this issue."
International policy experts say that the decision will also affect U.S. standing abroad.
"It will threaten our credibility in the world," said Nicholas Burns, a former U.S. diplomat and professor of international politics at Harvard University. "It may begin to create the impression that China is a more responsible country than the United States, and it might give a real boost to the Chinese because we will be seen as not doing our part on the biggest global problem."
But other top Republicans in both the House and the Senate had urged the president to keep the U.S. in the agreement.