Group of Eight leaders patched together a deal to fight climate change at a summit that wound up on Wednesday, but failed to convince big emerging economies that rich countries were doing enough.

Climate change was the most contentious topic at this year's G8 summit in Japan, which also tackled political problems from the crisis in Zimbabwe to worsening security in Afghanistan as well as soaring food and oil prices and poverty in Africa.

"There's been no huge breakthrough at this particular meeting, it is one step along the road," said Australian Prime Minister Kevin Rudd, who attended a climate change meeting on Wednesday where the G8 leaders were joined by eight more big polluters. "Of course, there's a long, long way to go."

That 16-member Major Economies Meeting group agreed that "deep cuts" in greenhouse gas emissions were needed to combat the global warming that is closely linked to rising prices already hitting vulnerable economies hard.

But bickering between rich and poorer countries kept most emerging economies from signing on to a goal of at least halving global emissions by 2050. Nor did the broader group come up with specific numbers for the interim targets they agreed advanced countries should set.

EU leader Jose Manuel Barroso, said, however, that to focus on the divisions would be missing the point.

"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."

The leaders of Japan, Britain, Canada, Germany, France, Italy, Russia and the United States had embraced the 2050 goal a day earlier, but stressed their countries could not do it alone.

PAPERING OVER GAPS

The rich countries had to paper over deep gaps just to get their own climate change deal, with Europe and Japan urging bolder action while the United States opposed promising firm targets without assurances big emerging economies will act too.

U.S. President George W. Bush said "significant progress" was made on climate change at the summit, while Japan and the European Union also lauded the outcome.

Environmentalists, though, saw nothing to cheer.

"It's the stalemate we've had for a while," Kim Carstensen, director of the WWF's global climate initiative, told Reuters.

Expectations for this week's summit talks on climate were always low.

Many are sceptical that any significant new steps to combat global warming can be made until a new U.S. president comes to office in January 2009. It was a view shared by South Africa, one of five big emerging economies collectively called the G5.

"Until there's a change in the position of the United States, South Africa's feeling is that it will be very difficult for the G5 to move forward because they will always be forced to work on that level of the lowest common denominator," South African Environment Minister Marthinus van Schalkwyk told reporters.

Developing countries, along with the European Union and green groups, say rich countries must take the lead and specify interim targets for how to reach the mid-century goal, which scientists say is the minimum needed to prevent dangerous global warming.

AFGHANISTAN, AFRICA

India told the major economies meeting that developed countries had not done enough.

"This must change and you (the G8) must all show the leadership that you have always promised by taking and then delivering truly significant GHG (greenhouse gas) reductions," Indian Prime Minister Manmohan Singh told the meeting.

The stance of emerging nations is important. The G8 nations emit about 40 percent of mankind's greenhouse gas emissions. China and India together emit about 25 percent of the total, a proportion that is rising as their coal-fuelled economies boom.

Leaders of the G8 countries agreed at the summit to impose sanctions against Zimbabwe's leaders because of violence during the widely condemned re-election of President Robert Mugabe.

"There should be no safe haven and no hiding place for the criminal cabal that now make up the Mugabe regime," Prime Minister Gordon Brown told a news conference after the summit.

The G8 also urged Afghanistan's government to take more responsibility for its own security and reconstruction, and pledged to increase assistance to that country's army and police.

Canadian Prime Minister Stephen Harper said members agreed with "unprecedented unanimity" about the need to do much more.

Some 900 soldiers in a U.S.-led coalition force have died in Afghanistan since 2001, among them 90 Canadians.

The G8 countries reassured sceptics on Tuesday that they were "firmly committed" to an aid target for Africa that was pledged at the Gleneagles summit in 2005.

Aid workers and NGOs have expressed concern that donor countries would fail to meet a G8 pledge to raise annual aid levels by $50 billion (25.3 billion pounds) by 2010, half of which was to go to Africa.

The G8 leaders also acknowledged the economic threat from surging oil and food prices, which could drive millions more into poverty, but came up with no fresh initiatives to tackle what they said were complex problems requiring long-term solutions.