"There has been major progress on the climate change agenda beyond what people thought possible a few months ago," he told reporters. "For the first time the G8 has said we will adopt at least a 50 percent reduction in carbon emissions by 2050 as part of a worldwide agreement that we hope to get in Copenhagen."
Summit host Japan also said the deal represented "significant progress" from last year and would boost momentum for the U.N.-led talks, although not all Tokyo's hopes had been met.
"Are we disappointed? Not really, because we have been able to achieve consensus among the G8," said Koji Tsuruoka, director general for global issues at Japan's foreign ministry.
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 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, 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 G8 said the steep rise in global food prices also threatened food security and called for countries with sufficient food stocks to make available a part of their surplus for countries in need.
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.
The G8 leaders reaffirmed aid targets pledged at their Gleneagles summit in 2005, when they vowed to raise annual levels of aid by $50 billion (25 billion pounds) by 2010, $25 billion of that for Africa.
Aid workers and NGOs had expressed concern about the pledge, saying donor countries might fail to meet their promises, which are not legally binding and are hard to track in actual spending.
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."
