The pact is named after Japan's ancient capital where the agreement was signed in 1997.

Outlining his "Cool Earth 50" proposals in a speech, Abe said a post-Kyoto framework should include all major emitters such as the United States, China and India. Kyoto's first phase ends in 2012 and negotiations have yet to start in earnest on the pact's next stage.

Abe said a post-2012 framework should also take into account the diverse conditions in different countries and be compatible with both economic growth and environmental protection.

"There is only one Earth, and there are no national boundaries for the air.

"Even the most outstanding strategy would be meaningless unless all people living on Earth participate in it," Abe said.

"If the framework required economic growth to be sacrificed, the participation of many countries cannot be expected."

Germany has been pushing for G8 members to commit to cutting greenhouse gas emissions by 50 percent below 1990 levels by 2050. But German Chancellor Angela Merkel said earlier on Thursday that she was unsure whether the G8 summit would produce a breakthrough in the fight against global warming.

The United States, which is the world's biggest emitter of greenhouse gases and pulled out of the Kyoto pact in 2001, has said it would keep rejecting targets or plans to cap emissions because it fears these steps could hurt economic growth.

Japan -- itself one of the world's top emitters of greenhouse gases -- will host next year's Group of Eight summit of wealthy nations and the environment will be a key issue there as well.

"ALL ABOARD"

The long-term target proposed by Japan would not be binding and does not specify a base year against which cuts would be measured, Koji Tsuruoka, director-general for global issues at Japan's foreign ministry, told reporters.

"When we talk about 2050 ... we do not have sufficient scientific knowledge to be concrete and precise in identifying a goal," he said.

"It is going to be a vision that could be shared as a target that could be accepted ... by all the countries of the world."

A centrepiece of Abe's proposal was a pledge to create a new form of financial aid to provide support for developing countries that, as he put it, "say 'No' to further global warming".

Other developed countries and international bodies such as the World Bank and United Nations could also take part, Abe said.

"Japan's intention is to have developing countries come on board in line with what we are proposing," Tsuruoka said.

But he added details had yet to be worked out on how the new aid mechanism would work or how much funding would be available.

Abe also launched a campaign to ensure Japan achieves its own target under the Kyoto Protocol of cutting its carbon dioxide emissions by 6 percent in the 2008-2012 period from 1990 levels.

Japan's actual emissions were 14 percent above its Kyoto goal as of March 2006.

The United States says Kyoto is unworkable because it excludes big developing nations such as India and China from binding targets during the treaty's first phase.