President Donald Trump is withdrawing the US from the Paris agreement on climate change, a UN treaty signed by almost 200 nations in 2016 and considered a major achievement by his predecessor, Barack Obama.

The decision was announced Thursday afternoon in the White House Rose Garden.

“In order to fulfill my solemn duty to protect America and its citizens, the US will withdraw from the Paris climate accord,” Trump said.

His administration will begin negotiations to reenter either the Paris accord or another climate treaty, “on terms that are fair” to the US, Trump added.

“As of today, the US will cease all implementation” of the Paris accord and the “draconian” burdens it mandated, he said.

Implementing the pact would have the US cost trillions of dollars and hundreds of thousands of lost industrial job, with massive reductions to the production of paper, cement, iron and steel, coal, and natural gas, Trump said, explaining his decision.

“This agreement is less about the climate and more about other countries gaining financial advantages over the US,” the president said.

The leaders of France, Germany and Italy released a joint statement less than an hour after Trump’s announcement, dismissing any opportunity for renegotiation and promising to step up their own support for the Paris Agreement.

“We deem the momentum generated in Paris in December 2015 irreversible and we firmly believe that the Paris Agreement cannot be renegotiated since it is a vital instrument for our planet, societies and economies," French President Emmanuel Macron, German Chancellor Angela Merkel and Italian Prime Minister Paolo Gentiloni said, according to Reuters.

In the absence of US funding, the three countries with the largest economies in Europe vowed to “step up efforts to support developing countries, in particular the poorest and most vulnerable, in achieving their mitigation and adaptation goals.”

Trump viewed the pact as putting the US' enormous wealth under lock and key, “leaving millions of families trapped in poverty and joblessness,” he said, pointing out that just two weeks of emissions from China alone would totally wipe out the gains from all US carbon reductions through 2030.

“The US, under the Trump administration, will continue to be the cleanest and most environmentally friendly country in the world,” but not at the cost of American prosperity, he added.

Negotiated in 2015, the Paris agreement seeks to drastically limit carbon dioxide and other emissions from fossil fuel consumption, in order to slow down global warming. The US was committed to reducing emissions by up to 28 percent from 2005 levels by 2025. China is currently the world’s biggest carbon emitter, with the US trailing close behind.

Of the top 3 CO2 emitters, China, US, EU - #Trump only leader to pull country from the #ParisClimateDealhttps://t.co/Djgsa0L37lpic.twitter.com/qFELXcAPO6 — RT America (@RT_America) June 1, 2017

The international climate summit that was supposed to take place in Boston next month has been canceled due to lack of federal support, Mayor Martin J. Walsh said Wednesday.

“The administration just hasn’t been responding to us to see if they’re interested in working on bringing folks here,” Walsh said at a news conference. “It doesn’t seem like there’s any interest at all in moving forward.”

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Back in 2012, Trump derided global warming as a Chinese hoax to make the US de-industrialize. During the Republican primary campaign, he told the Washington Post he was “not a big believer in man-made climate change.”

In a May 2016 campaign speech on energy policy, Trump said he would “cancel” the Paris treaty.

"Any regulation that's outdated, unnecessary, bad for workers or contrary to the national interest will be scrapped and scrapped completely," he said.

The administration is now deciding whether to initiate a full, formal withdrawal from the treaty - a process that could take as much as 3 years - or leave the UN climate change treaty altogether.

Canada, the European Union, and China have said they will honor their commitments to the pact even if the US withdraws, Reuters reported.

"China will stand by its responsibilities on climate change," Premier Li Keqiang told reporters after meeting German Chancellor Angela Merkel in Berlin on Tuesday.

Merkel called the Paris agreement "essential."

Russia likewise remains committed to the treaty, to which Moscow "attaches great significance," Kremlin spokesman Dmitry Peskov said Thursday.

Don't know which way Paris will go, but I've done all I can to advise directly to POTUS, through others in WH & via councils, that we remain — Elon Musk (@elonmusk) May 31, 2017

Speculation was rife as to who might have influenced the president's decision, with Reuters describing EPA administrator Scott Pruitt and adviser Steve Bannon as being in favor of pulling out, while Trump's daughter Ivanka, chief economic adviser Gary Cohn and Energy Secretary Rick Perry wanted the US to remain.

'We believe that the mitigation of climate change is essential for the safeguarding of our investments' https://t.co/jl3hOzQfxL — RT America (@RT_America) May 8, 2017

Over two dozen leading world corporations - including Apple, Facebook, Google and Microsoft - sent a letter to Trump on Wednesday, “strongly urging” him to remain in the Paris pact and saying it was beneficial to both the economy and the environment.