Leaks of the draft statement for the July 7-9 summit in Japan suggest that rich nations will water down commitments to help Africa and offer little new on cutting greenhouse gas emissions.

Ban, in Tokyo on the first leg of an Asian tour, said that wealthy nations should lead the campaign on the "triple crisis" of climate change, poverty and rising food prices.

"They have the capacity, they have the resources and I hope the leaders will demonstrate their political will," Ban told a news conference in Tokyo.

Reports have said that the draft statement of the G8 summit -- which brings together Britain, Canada, France, Germany, Italy, Japan, Russia and the United States -- will not cite a specific figure on development aid.

The 2005 G8 summit in Gleneagles, Scotland, called for a doubling of rich nations' foreign aid by 2010 to 50 billion dollars, half of it to Africa.

"What I would like to urge and emphasise is that the leaders of the G8 should implement their commitment which was made in Gleneagles," Ban said.

"There are so many poor people in the world and there are so many people who do not have access to decent medical facilities and there are so many people who are not given education opportunities," Ban said.

"Therefore it is absolutely necessary that the leaders of the G8 should lead this campaign."

Ban later left for China, his second stop on a three-nation tour that will also take him to his native South Korea. He will return to Japan for the G8 summit in the northern mountain resort of Toyako.