Washington (CNN) President Donald Trump proclaimed Thursday he was withdrawing the US from the Paris climate accord , a sweeping step that fulfills a campaign promise while acutely dampening global efforts to curb global warming.

Speaking from the White House, Trump said he was open to renegotiating aspects of the agreement, which was inked under his predecessor and which all nations except two have signed onto.

But he was withering in his criticism of the pact, which he cast as a humiliating defeat for American workers that unfairly advantaged foreign countries.

"At what point does America get demeaned? At what point do they start laughing at us as a country?" Trump inquired during an afternoon event held in a sun-drenched Rose Garden.

"We want fair treatment," Trump said. "We don't want other countries and other leaders to laugh at us anymore."

The decision amounts to a rebuttal of the worldwide effort to pressure Trump to remain a part of the agreement, which 195 nations signed onto. Foreign leaders, business executives and Trump's own daughter, Ivanka, lobbied heavily for him to remain a part of the deal, but ultimately lost out to conservatives who claim the plan is bad for the United States.

Trump, who has governed with an "American First" policy, said Thursday he was carrying out the will of the voters who propelled him to the White House.

"I was elected by the citizens of Pittsburgh," Trump said, "not Paris."

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Lengthy process

In triggering the official withdrawal procedures, Trump has sparked a lengthy process that won't conclude until November 2020 -- the same month he's up for reelection, ensuring the issue becomes a major topic of debate in the next presidential contest.

In his remarks, Trump said he was open to re-brokering US carbon reduction commitments, but didn't express any urgency in bringing the US back into the deal, which he claimed placed "draconian" financial burdens on the American people.

"We're getting out," he said. "And we will start to renegotiate and we'll see if there's a better deal. If we can, great. If we can't, that's fine."

Afterward, the leaders of France, Italy and Germany indicated in a joint statement that the US could not unilaterally renegotiate the agreement. The UN body that facilitated the deal said it "cannot be renegotiated based on the request of a single party."

Briefing reporters, White House officials would not specify what parameters would be acceptable to Trump in a new accord.

"When we talk about what a better deal looks like, that's up to the President," said one White House aide.

Trump said his announcement would end the implementation of carbon reduction targets set under Obama, which aimed to reduce emissions by 26-28% in a decade. Trump also declared the US would stall all contributions to the United Nations' Green Climate Fund, which Trump said was "costing the United States a fortune."

"As someone who cares deeply about our environment, I cannot in good conscience support a deal which punishes the United States," he said. "The Paris accord is very unfair at the highest level to the United States."

The President campaigned ardently against the climate agreement last year as a candidate, vowing to "cancel" the accord. Those close to him said he was insistent upon fulfilling his promises, despite urging from some members of his own administration to remain in the agreement.

A person familiar with Trump's thinking said the President was convinced he needed to withdraw from the pact, and there was little chance of talking him out of it.

Opponents of the move say it threatens to isolate the United States in a global effort to curb the warming of the planet, and leaves an opening for countries like China to fill the leadership void.

Uncertainty loomed

Trump's announcement Thursday ends months of speculation about his intentions. The uncertainty over Trump's decision lent the Rose Garden announcement a reality show-like air, with Thursday's unveiling acting as a finale to a months-long debate that has split members of the President's inner circle and led to deep consternation from global allies.

The show-like atmosphere was fueled by the presence of a jazz band, which performed a series of numbers before Trump emerged from the Oval Office to deliver his statement.

The announcement concluded a long and bitter dispute among West Wing aides to sway Trump's thinking. Ivanka Trump had worked to ensure her father heard pro-Paris voices over the last several months, and even in recent days continued to press for a decision short of a full withdrawal.

Ivanka Trump and her allies, including Secretary of State Rex Tillerson and Trump's chief economist Gary Cohn, pressed Trump to alter the US commitments to the Paris agreement without fully pulling out of the accord. Trump was also pressured heavily by his foreign counterparts during last week's G7 meetings in Sicily to remain in the deal, though his advisers say he felt little obligation to concede to that point of view.

In the end, anti-Paris voices, led by chief strategist Steve Bannon and EPA administrator Scott Pruitt, won out, and Trump's remarks Thursday reflected the nationalist viewpoints espoused by Bannon and his cohorts.

"This agreement is less about the climate and more about other countries gaining a financial advantage over the United States," Trump said.

Bannon was seated in the front row of the audience during Trump's remarks, while Pruitt delivered a statement himself after Trump spoke. Ivanka Trump wasn't not present for the announcement; aides said she was at home celebrating the Jewish holiday of Shavuot.

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Critics pounce

After Trump's announcement, business leaders, politicians, and foreign heads-of-state began castigating the decision as a woeful abandonment of US leadership.

In a rare statement about current political events, former President Barack Obama, whose administration negotiated the Paris accord, wrote Trump's decision would leave American workers behind those in countries who remain a part of the agreement.

"The nations that remain in the Paris Agreement will be the nations that reap the benefits in jobs and industries created," Obama wrote. "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 multiple foreign leaders decried the decision, including in phone calls directly with Trump. Canadian Prime Minister Justin Trudeau told Trump his was disappointed in his decision, according to a statement from his office. French President Emmanuel Macron informed Trump that the Paris accord could not be negotiated, the Élysée Palace said.

Meanwhile, China, the world's largest carbon emitter, has said it will stick by its commitments to the Paris agreement, despite the US moves.