Washington - President Donald Trump on Thursday said he will withdraw the United States from the landmark 2015 global agreement to fight climate change, spurning pleas from US allies and corporate leaders in an action that fulfilled a major campaign pledge.

"We're getting out," 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," Trump said. But he added that the United States 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."

With Trump's action, the United States 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 United States with Syria and Nicaragua as the world's only non-participants in the accord.

The United States was one of 195 nations that agreed to the accord in Paris in December 2015, a deal that former US President Barack Obama was instrumental in brokering.

Supporters of the accord condemned Trump's move as an abdication of American leadership and an international disgrace.

"At this moment, when climate change is already causing devastating harm around the world, we do not have the moral right to turn our backs on efforts to preserve this planet for future generations," said US Senator Bernie Sanders, who sought the Democratic presidential nomination last year.

"Ignoring reality and leaving the Paris agreement could go down as one of the worst foreign policy blunders in our nation's history, isolating the U.S. further after Trump's shockingly bad European trip," Democratic Senator Sheldon Whitehouse added.

Under the pact, which was years in the making, nations both rich and poor committed to reducing emissions of so-called greenhouse gases generated by burning fossils fuels and blamed by scientists for warming the planet.