US President Donald Trump has announced that the United States will withdraw from the Paris climate agreement, following through on a pledge he made during his presidential campaign.

"We're getting out," Mr Trump said at a ceremony in the White House Rose Garden in which he decried the Paris accord's "draconian" financial and economic burdens.

"In order to fulfill my solemn duty to protect America and its citizens, the United States will withdraw from the Paris climate accord," he said.

But he added that the US would begin negotiations to re-enter either the Paris accord or "a new transaction on terms that are fair to the United States, its businesses, its workers, its people, its taxpayers."

The former businessman said that the current deal is not tough enough on countries such as China and India.

He added that the US will cease all implementation of non-binding elements of the accord "as of today."

With Mr Trump's action, the US will walk away from nearly every nation in the world on one of the pressing global issues of the 21st century.

The pullout will align the US with Syria and Nicaragua as the world's only non-participants in the accord.

Mr Trump's predecessor, Barack Obama, said the current administration rejects the future in pulling out of the pact.

"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," Mr Obama said in a statement.

Tesla's Elon Musk also announced that he is leaving Mr Trump's presidential council, saying "climate change is real."

Minister for the Environment Denis Naughten said he was "extremely disappointed and concerned" by the announcement.

In a statement, he said "this is a major setback for the international community and it is essential that the decision of the United States does not weaken global resolve."

The leaders of France, Italy and Germany have also criticised the decision, as well as rejecting Mr Trump's assertion that the pact could be revised.

The US withdrawal comes less than 18 months after the historic 196-nation pact was signed in the French capital - the fruit of a hard-fought agreement between China and the US under Barack Obama's leadership.

The European Union and China have indicated they would press ahead with the deal, regardless of US participation.

The US is the world's second biggest carbon emitter, after China.

"China and the EU ... will implement the agreement," a senior EU official told reporters, on condition of anonymity.

"The Paris Agreement will continue with full force of implementation even if the US pulls out."

Since taking office on 20 January, Mr Trump sent contradictory signals on the Paris deal - reflecting the different currents within his administration, both on climate change but also on the wider issue of America's role in the world and its position on multilateralism.

When asked on Tuesday whether Mr Trump believes human activity is contributing to climate change, White House spokesman Sean Spicer told reporter: "Honestly, I haven't asked him that. I can get back to you."

The head of the Environmental Protection Agency, Scott Pruitt, who met with Mr Trump on Tuesday, has overtly advocated quitting a deal he judges "bad" for the US.

But other top Trump advisers, including daughter Ivanka and Gary Cohn, the head of the president's National Economic Council, were said to favour staying in the treaty.

The corporate world has by-and-large come out in favour of the US keeping its seat at the table.

A dozen large groups including oil major BP, agrochemical giant DuPont, Google, Intel and Microsoft, urged Mr Trump to remain part of the deal.

Mr Trump's position on the accord was a focal point of last week's G7 summit in Sicily, at which leaders of the world's six other leading economies pressed him to renew the US commitment to the deal.

A frustrated German Chancellor Angela Merkel later warned that Europe "must take its fate into its own hands," citing the differences with Washington on climate change as evidence of their divergent paths.

She described the discussion as "very difficult, not to say very unsatisfactory".

US Defence Secretary Jim Mattis responded in a television interview on Sunday, assuring that  Mr Trump was "wide open on this issue as he takes in the pros and cons of that accord".

Mr Cohn, who is Mr Trump's economic adviser, also said last week that the president's views were "evolving".

Analysis - Environment Correspondent George Lee

The agreement is an historic and unprecedented collaboration among 196 nations and states. Although it was agreed in Paris in December 2015 the deal was years in the making.

It is in effect an agreement that we must all face the climate change challenge together, and every country has a responsibility to play a part.

More is expected from richer and more developed countries, while poorer and less developed countries are to be helped to play their part and helped also to adjust to the effects of climate change.

It is by no mean perfect but, all things considered, it represents a solid plan which, if followed, is humanity's best chance of preventing the devastation of runaway climate change by the end of this century.

Included in the agreement is:

  • A commitment to limit global warming to well below 2 degrees, and as close as possible to 1.5 degrees Celsius.
  • hat countries will take all necessary actions to peak their emissions as soon as possible, then rapidly reduce them, and progressively increase their commitments every five years
  • Developed countries are to provide €100bn per year to help poor countries affected by climate change, and more after 2025.
  • And there is to be a new transparency framework and expert reviews to hold countries to account.