TOYAKO, Hokkaido — The Group of Eight leaders gave the green light Tuesday to expanded development of nuclear power, saying it is a vital energy source in the fight against global warming.

But they warned that further development of nuclear plants must adhere to nonproliferation standards.

"A growing number of countries have expressed interest in nuclear power programs as a means to addressing climate change and energy security concerns. These countries regard nuclear power as an essential instrument in reducing dependence on fossil fuels, and hence greenhouse gas emissions," the leaders said in a statement on environment and climate change.