The Obama-era official who helped deliver the 2015 Paris Agreement, lashed out Thursday at the Donald Trump administration's "wrongheaded" decision to abandon the first-ever pact committing all countries to limiting climate change.

Todd Stern, who was Barack Obama's special envoy for climate change, said he was "annoyed, frustrated" by the new president's rejection of a deal that took the world's nations more than two decades to negotiate.

"It's completely wrongheaded thing to do," Stern, who left the state department in 2016, told AFP on the sidelines of a UN climate conference in Bonn which he attended as an observer.

"Climate change is a huge challenge, we all know that," he said.

"We are in a... race against time to transform the economy faster than the bad stuff of climate change," he said.

"Trying to say it's a hoax, or it doesn't mean anything, or it's a terrible agreement  and the rest of the world is laughing at us, is just so.. ridiculous."

Obama was a champion of the deal which America ratified just two months before Trump, who has described climate change as a "hoax", was elected to the White House.

Trump announced in June that America would abandon the pact, but the rules determine this cannot happen until November 2020.

The United States is the world's biggest historical greenhouse gas polluter, and second only to China for current-day emissions.

This week, Syria became the 196th country to formally adopt the Paris Agreement, leaving America as the only nation in the UN climate convention to reject it.

The pact commits countries to limiting average global warming to under two degrees Celsius (3.6 degrees Fahrenheit) over Industrial Revolution levels, and 1.5 C if possible, to avert calamitous climate change-induced storms, drought and sea-level rises.

To bolster the agreement, nations submitted voluntary commitments to curb emissions.

But the 1 C mark has already been passed, and analysts say the world is headed for a 3 C-warmer world, or more, on current country pledges.

- 'More angry than sad' -

While waiting to exit the deal, Washington is participating in the UN climate talks, where envoys are working out "rules" for putting the agreement into action.

Not all have welcomed the presence of the Americans in their midst, and Stern said Trump's decision "inevitably undermines the credibility and... strength of the US team."

He also criticised the White House hosting a sideline event at the talks on Monday, where administration officials and energy company executives defended continued fossil fuel use.

"Do I think it's constructive to do an event on coal? No, obviously not," said Stern, now a senior fellow with the Brookings Institution, a Washington-based think-tank.

Having invested more than seven years in negotiating the Paris Agreement, Stern said he felt "more angry than sad" at the way things have turned out -- "annoyed, frustrated".

"Ideologues thought it was a good idea, and some of the president's so-called base supporters thought it was a good idea, but you have to look pretty hard to find informed people, companies... who thought that was a good idea," he said.

Source: AFP