The Group of Eight wrapped up three days of talks in a secluded mountain resort in Japan by inviting leaders of growing emerging economies such as China and India for a special session summit on global warming.

US President George W. Bush hailed the summit as "very productive" as he left the scenic venue. "I'm pleased to report that we've had significant success," he said.

But the final hours of the meeting were overshadowed by Iran's testing of its Shahab-3 missile that can reach Israel.

The White House denounced the test and warned the Islamic republic to abandon its ballistic missile programme immediately.

"Iran's development of ballistic missiles is a violation of United Nations Security Council resolutions and completely inconsistent with Iran's obligations to the world," said White House spokesman Gordon Johndroe.

The leaders of the G8 nations, which together account for two-thirds of the world's gross domestic product, said in a joint statement that while global growth had "moderated," they were positive on the future.

They called for efforts to bring down oil prices, which have jumped five-fold since 2003, as well as the soaring cost of food which has set off riots in parts of the developing world.

"There's a need to improve transparency on the oil market," Japanese Prime Minister Yasuo Fukuda told a news conference at the end of the summit with leaders of Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.

G8 leaders also called on all countries to end export restrictions on food, Fukuda said.

The summit was dominated by discussions on global warming amid growing concern that rising temperatures caused by carbon emissions are threatening entire species of plants and animals.

The rich nations' club on Tuesday agreed on the need for a global emissions cut of at least 50 per cent by 2050, a step praised by G8 leaders as a step forward after years of hesitation by Bush.

But developing countries slammed the statement as too weak, tussling with rich nations at a special expanded summit on Wednesday bringing together the G8 with eight other leaders including Chinese President Hu Jintao and Indian Prime Minister Manmohan Singh.

The deadlock between rich and developing nations has held up talks on reaching a new climate treaty by the end of 2009 in Copenhagen -- a goal set in December at a UN-backed conference in Bali.

"Climate change is one of the great global challenges of our time," the 16 leaders said in a statement. "Our nations will continue to work constructively together to promote the success of the Copenhagen climate change conference."

But their statement said only that rich countries would implement their own goals for cutting greenhouse emissions while developing major economies would also take action, without proposing any numbers.

European Commission president Jose Manuel Barroso defended the summit outcome.

"It is quite wrong to see this in terms of a confrontation between developed and developing countries," he said. "Of course we accept the lion's share of responsibility but this is a global challenge which requires a global response."

Dan Price, assistant to Bush for international economic affairs, praised the US-initiated meeting Wednesday as useful.

"There was universal recognition that having these countries in the room, trying to find common ground, was an enormous contribution to the UN negotiations," he said.

But the so-called Group of Five -- Brazil, China, India, Mexico and South Africa -- has demanded that rich nations take the lead, saying they were historically responsible for climate change.

"Until there's a change in the decision of the United States, South Africa finds it very difficult for the G5 to move forward," South African Environment Minister Marthinus Van Schalkwyk told reporters.

Kim Carstensen, head of the WWF environmental group's Global Climate Initiative, accused rich nations of trying to stall action by putting the onus on developing countries.

"Some rich nations get lost in tactics and seem to forget that the survival of people and nature crucially depends on their leadership," he said.

The United States is the only major industrial country to reject the Kyoto Protocol, with Bush arguing that it is unfair by making no demands of fast-growing emerging economies.

French President Nicolas Sarkozy said that Tuesday's agreement meant the G8 "now has made a commitment" on cutting emissions but that emerging economies have not done the same.

"The United States is making a commitment, firmly and absolutely, with the condition imposed by their Congress that China and India also take action in a differentiated way," Sarkozy told reporters.