"I am deeply concerned about what President Trump of (the) United States has declared that the US is withdrawing from this Paris agreement.
"I have been speaking out that his vision is politically short-sighted, and economically irresponsible and scientifically wrong. So he is standing on the wrong side of history," Ban said on the sidelines of a London peace walk.
The former Secretary-General of the United Nations joined other members of The Elders, a group created by Nelson Mandela, on the procession through the city before a discussion on world peace.
Ban said despite Trump's decision to pull out of the historic Paris agreement, he remained heartened by a US civil society campaign to continue to honour the environmental deal.
"I am encouraged and hopeful that whole worlds will be united in moving ahead with this Paris climate change agreement. This is the political and moral responsibility of our political leaders," he said.
Trump announced in June the start of a three-year process to pull out of the 2015 agreement, signed by 195 countries, on the grounds that it would put the US at an economic disadvantage.
Ban also decried the current "lack of commitment" to an international spirit.
"A lack of leaders' global vision that we are living in a very tightly-interconnected small world, and that whatever is happening in this country may affect the neighbouring countries and even all around the world," he said.
He cited the "very tense period" on the divided Korean peninsula -- with Pyongyang staging its sixth nuclear test and launching two intercontinental ballistic missiles -- as one area where world leaders needed to act collectively.
"As one of the Korean citizens, I'm very much committed that the whole international community should stand resolute and unified and strong voices, so that North Korea realises that there is no other way but to return to dialogue to address these issues," he said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)