The dramatic announcement came as a summit of G7 leaders in Sicily wrapped up in deadlock on the issue, with United States partners voicing frustration at the president's failure to commit to the deal aimed at stemming global warming.
Trump, who for months has delayed a decision on the climate agreement, made his announcement at the conclusion of the G-7 summit in Taormina, Italy.
"This is not fair to the people and taxpayers of the United States", Mr. Trump said.
Tearfund's Head of Advocacy, Paul Cook, said: "While Tearfund welcomes the continued strong commitment from six of the Heads of State, to tackle climate change, we are disappointed that the United States could not reach a consensus".
German Chancellor Angela Merkel dubbed the summit that was supposed to decide on the ratification of climate deal, as "dissatisfying".
Recently elected President of France Emmanuel Macron seemed optimistic, saying he was certain Trump would support the agreement after conversations at the summit.
Robertson warned that the Canadian government and provinces need to be mindful of competitiveness when it comes to climate policy, but noted that many companies are already making changes with the environment in mind.
The Trump administration is reported to be divided on the issue.
Cohn, along with Ivanka Trump, Jared Kushner, and Secretary of State Rex Tillerson favor the agreement, while Environmental Protection Agency Administrator Scott Pruitt are against it. Pruitt was reportedly among those in which Trump confided that he intends to withdraw from the Paris Agreement.
Gary Cohn, Trump's chief economic adviser, told reporters at the summit that Trump "continues to study" the Paris agreement.
Leaders from the United States, Canada, Britain, France, Germany, Italy, and Japan gathered in the town of Taormina, Sicily, on Friday and Saturday.
Environmental groups were critical of the USA stance and praise for the other six countries to stand by their stances on the Paris deal. Then Obama led the way in forging and signing on to the Paris accords.
While at the G7 summit, Trump was heavily lobbied to endorse the Paris Climate Agreement, but he declined to do so.
"He stands in stark isolation", said Alden Meyer, who has followed climate talks for two decades as director of policy at the Union of Concerned Scientists.
The meeting's final declaration reflected a stalemate between the U.S. and the six other participating countries, which are all strongly committed to the Paris accord.
Trump has previously expressed skepticism about climate change.
The rift is one of several emerging disagreements between Trump and other world leaders.