"In order to protect American jobs, companies and workers, we've withdrawn the United States from the one-sided Paris Climate Accord," Trump said in a speech on the future of the US energy sector.
He was greeted with applause.
"I will tell you we're proud of it," he went on. "And when I go around, there are so many people that say thank you. You saved the sovereignty of our country."
The US might be "back into it some day", he said. "But it will be on better terms, it will be on fair terms."
Climate change is set to be a bone of contention between the US and other Western countries at the G20 talks in Hamburg, Germany, next week.
German Chancellor Angela Merkel on Thursday vowed to seek a clear commitment to fight global warming at the 7 July summit.
The Cop21 deal reached in Paris in 2015 is "non-negotiable", she said.
Having dubbed climate change a Chinese hoax during last year's presidentieal electioin campaign, Trump announced US withdrawal from the Paris deal on 1 June.The US is the world's second largest emitter of greenhouse gases after China.
Failure to take decisive action against climate change, will mean the US becoming a poorer country facing more dramatic inequality, according to a study published Thursday.
The poorest third of US counties could see income drops as great as 20 percent if current trends continue, according to the worst-case projection of the study based on 116 projections of climate change impact, published in the journal Science.