In his first major address on the subject of climate change since taking office in January, Ban also warned that climate change -- including droughts and coastal flooding -- could spark new conflicts and wars over shrinking resources.
And he said the absence of decisive measures to combat climate change now could place a huge burden on succeeding generations.
Underlining his concerns, the UN secretary-general said he would raise the issue of climate change at a summit of the Group of Eight (G8) major industrialized nations in Germany in June.
And he urged the United States, one of the world's biggest emitters of greenhouse gases, to immediately take the lead in the fight against global warming.
"I hope that United States, while they have taken their role in innovative technologies as well as promoting cleaner energies, will also take the lead in this very important and urgent issue," he said.
Ban said the world needed a more coherent system of international environmental governance in order to tackle global warming beyond the expiry of the Kyoto Protocol in 2012.
The 1997 protocol requires 35 industrial nations to cut their global-warming gases by an average 5 percent below 1990 levels by 2012.
The Bush administration has not signed the Kyoto protocol, saying its provisions would hurt the U.S. economy. Instead, Washington says it is spending almost $3 billion a year on energy-technology research and development to combat climate change.
Still, U.S. President George W. Bush has referred to global warming as an established fact. In his State of the Union speech in January, he acknowledged climate change needs to be addressed.
The United Nations will hold a conference on climate change in Bali in December.
An Increasingly Thirsty World
An Iraqi boy drinks from a waste-water reservoir near Baghdad (epa file photo)
A MATTER OF LIFE AND DEATH. Disputes about access to water are increasingly coming to the center of global attention, especially in China, India, and Central Asia. Writing about the 1967 Six Day War in his 2001 memoirs, Israeli Prime Minister Ariel Sharon said that "while border disputes between Syria and ourselves were of great significance, the matter of water diversion was a stark issue of life and death." (more)