In a communique released during a summit in northern Japan, the Group of Eight leaders agreed that they would need to set interim goals on the way to a "shared vision" for 2050 although it gave no numerical targets.

Mention of mid-term goals was an advance from last year when the G8 agreed only to "seriously consider" a goal of halving emissions by mid-century.

But calling on countries involved in U.N. negotiations on climate change to also "consider and adopt" the 2050 goal satisfies the United States, which has said it cannot agree to binding targets unless big polluters such as China and India rein in their emissions too.

Dan Price, assistant to the president for international economic affairs, described the G8 declaration on climate change as "an excellent discussion, and an excellent declaration" and he said that "significant progress" was made.

Price said the statement reflected that "the G8 alone cannot effectively address climate change, cannot effectively achieve this goal, but that contributions from all major economies are required".

Critics outside the rich nations' club slammed the deal. Environmental campaign group WWF said the leaders had ducked their responsibilities.

"The G8 are responsible for 62 percent of the carbon dioxide accumulated in the Earth's atmosphere, which makes them the main culprit of climate change and the biggest part of the problem," WWF said shortly after the statement was issued.

"WWF finds it pathetic that they still duck their historic responsibility," the campaign group said in a statement.

The European Union and Japan had been pressing for this year's summit to go beyond just "considering" the 2050 goal, and Brussels had wanted clear interim targets as well.

South African Environment Minister Marthinus van Schalkwyk said he feared this year's communique was a step backward.

"While the statement may appear as a movement forward, we are concerned that it may, in effect, be a regression from what is required to make a meaningful contribution to meeting the challenges of climate change," van Schalkwyk said.

The U.N.-led talks aim to create a new framework for when the Kyoto Protocol expires in 2012 and are set to conclude in Copenhagen in December 2009.

The G8 comprises Japan, Britain, Canada, Germany, France, Italy, Russia and the United States.

FOOD AND FUEL

Global warming ties into other big themes such as soaring food and fuel prices being discussed at the three-day summit at a plush mountain-top hotel on the northern Japanese island of Hokkaido, where 21,000 police have been mobilised.

In another statement released on the second day of the summit, the leaders expressed strong concern about sky-high food and oil prices, which they said posed risks for a global economy under serious financial strain.

The group also made a thinly veiled call for China to let the yuan's tightly controlled exchange rate appreciate to help reduce global financial imbalances.

"In some emerging economies with large and growing current account surpluses, it is crucial that their effective exchange rates move so that necessary adjustment will occur," the G8 said in the statement.

The leaders agreed to bring major oil producers and consumers together in a new forum to discuss energy security. One diplomat said it would also be a venue to talk about output and prices.

The price of food and of oil, which hit a record high of $145.85 a barrel last week, is taking a particularly heavy toll on the world's poor.

A World Bank study issued last week said up to 105 million more people could drop below the poverty line due to the leap in food prices, including 30 million in Africa.

To help cushion the blow, officials said the G8 would unveil a series of measures to help Africa, especially its farmers, and would affirm its commitment to double aid to $50 billion by 2010, with half to go to the world's poorest continent.

The summit has become a magnet for protesters and although Japan has been effective at cracking down on any demonstrations -- helped by the remote location of the summit -- a few thousand have managed to hold protests several km (miles) away.

A group of demonstrators marched to the sound of music and drums on Tuesday, holding signs saying "Smash the G8 summit" and "Free G8 political prisoners".

Tomoyuki Sueoka, a 25-year-old graduate student, said: "G8 nations do not have the right to decide the policies of the world. This is not democratic. They talk about poverty and food shortages but they are simply talking about business."

The summit wraps up on Wednesday with a Major Economies Meeting comprising the G8 and eight other big greenhouse gas-emitting countries, including India, China and Australia.