UN chief Ban Ki-moon has said it represents as big a threat to mankind as war and vowed to raise the issue at a summit of rich nations in June.[File photo:AFP/Don Emmert]

Responding to mounting pressure to speak out on climate change, UN chief Ban Ki-moon has said it represents as big a threat to mankind as war and vowed to raise the issue at a summit of rich nations in June.

Since a damning United Nations report warned last month that global fossil fuel-related pollution would raise temperatures this century, melt polar ice and worsen floods, droughts and hurricanes, Ban had been urged by environmentalists to lead a drive for world action to roll back global warming.

In a speech to international high school students here, he said Thursday that "the danger posed by war to all of humanity -- and to our planet -- is at least matched by the climate crisis and global warming."

And he pledged to raise the issue at a summit of the Group of Eight (G8) group of major industrialized nations in Germany in June, saying failure to take decisive measures to combat climate change would place an appalling burden on succeeding generations.

"That would be an unconscionable legacy; one which we must all join hands to avert," he said. "As it stands, the damage already inflicted on our ecosystem will take decades, perhaps centuries, to reverse -- if we act now."

Referring to the G8 summit in Germany, Ban stressed that the task of tackling climate change was beyond the capacity of any one nation.

"These issues transcend borders," he said. "Only concerted and coordinated international action, supported and sustained by individual initiative, will be sufficient."

During an African tour in late January, Ban already underscored the UN's leading role in tackling climate change which he described as "a scientifically proven fact" and called for concrete measures to combat it.

In Nairobi, he met with UN Environment Programme (UNEP) chief Achim Steiner, who lobbied for a summit on climate change later this year.

Environmentalists hope to hold the meeting between the G8 summit and the next meeting in Bali of signatories to the Kyoto Protocol on global warming in December.

In his speech to the students, Ban reiterated that action on climate change would be one of his top priorities and welcomed a growing awareness of the issue in industrialized countries.

"In increasing numbers, decision makers are recognizing that the cost of inaction or delayed action will far exceed the short-term investments needed to address this challenge," he noted.

And alluding to the Oscar award for former US vice president Al Gore's documentary "An Inconvenient Truth" late last month, Ban said it "suggests that, even amongst the broader public, climate change is no longer an 'inconvenient' issue, it is an inescapable reality."

"Now, each one of us also needs to commit to the search for solutions. We have to change the way we live, and rethink the way we travel and transact business," he added.

In the United States, which is responsible for 25 percent of global carbon dioxide emissions, the Democratic-led Congress is preparing to draft legislation to combat climate change.

Democratic lawmakers have also accused Republican President George W. Bush's administration of muzzling government-employed climatologists.

Bush has continued to favor an approach based on voluntary measures, believing that imposing reductions could have disastrous economic consequences.

But alarm about the perils of global warming has been growing among US scientists, business people and some individual states.

California, the most populous and most economically influential US state, recently decided to impose a carbon-dioxide emissions reduction.