TOYAKO, Hokkaido — The three-day Group of Eight summit in Toyako, Hokkaido, concluded Wednesday as the major industrialized powers and key emerging economies agreed to jointly fight global warming but failed to set any quantitative goals to substantiate their pledge.

"We, the leaders of the world's major economies, both developed and developing, commit to combat climate change in accordance with our common but differentiated responsibilities and respective capabilities," said a joint statement by the G8 states and eight other major greenhouse gas-emitting countries.

But five of the eight non-G8 participants — namely China, India, Brazil, South Africa and Mexico — turned down the G8's call to share a target to halve global emissions of greenhouse gases by 2050, a goal that was barely agreed on by the industrial countries the previous day.