Leaders at the July 7-9 summit are expected to formalise a goal of halving global emissions by 2050 after agreeing last year in Germany to seriously consider the target.

Pressure is also mounting from environmentalists and emerging economies for the G8 to come up with medium-term targets on the way to that goal. But wide gaps exist within the group and between rich and poorer nations over how to share the burden of fighting climate change, which causes droughts, rising seas and more severe storms.

"As for medium-term targets, this is the core challenge for UN negotiations until the end of 2009. The G8 is not a forum to agree on that target," Fukuda said in an interview with news agencies ahead of the summit.

"We will strive to engage in constructive discussions so we can come up with concrete outcomes including a long-term target," he said, but added: "What is important is that all major economies participate in a responsible manner."

Fukuda last week unveiled Japan's own plan to reduce emissions by 60-80 percent from current levels by 2050 and begin a trial system for carbon trade.

But he stopped short of setting an interim goal, saying that step would come next year as part of UN-led negotiations that aim to agree by December 2009 on a successor to the Kyoto Protocol, which expires in 2012.

Signs have been growing that the United States was against a more ambitious outcome in Hokkaido.

The United States has said it will accept binding emissions curbs, but only if major developing emitters such as China and India also agree, something they have so far refused to do.

SOARING FOOD, OIL PRICES

Washington wants the main forum for climate talks in Hokkaido to be a major economies meeting to be held on the sidelines of the G8 summit, bringing together G8 with Australia, Brazil, China, India, Indonesia, Mexico, South Korea and South Africa.

Climate change was meant to be at the centre of the Group of Eight (G8) summit but soaring food and fuel prices have muscled their way onto the agenda.

G8 finance ministers warned last weekend that soaring commodity prices could slice economic growth, but shrank from offering any plan to calm markets or quell protests over the cost of food and fuel. [ID:nSP21490]

"It is a complicated issue which cannot be solved in the short term," Fukuda told a group of news agencies in an interview ahead of a G8 leaders' summit meeting.

"The G8 needs to set the direction by sending a message."

Hosting the summit just might be the highlight of Fukuda's career -- he has long appeared to favour the nuances of foreign policy over rough-and-tumble domestic politics. But his sagging popularity is making it hard to show bold diplomatic leadership.

The 71-year-old moderate's public support ratings have slid since he took office last September on doubts about his ability to cope with a divided parliament where the opposition controls the upper house and can delay laws and block appointments, although recent polls suggest the slide might be bottoming out.

Speculation has been simmering that the ruling bloc might seek to replace him with a more popular politician to improve the its prospects in a general election that must be held after lawmakers' terms expire in September 2009.

Some pundits think Fukuda might call a snap election for the lower house later this year or early in 2009 to try to win a mandate to break the political deadlock, but on Tuesday he denied he had such a tactic in mind.

That was hardly surprising after two polls issued on Tuesday showed more voters would opt for the opposition if a election was held now.