"I don't think any good outcome will be achieved by hitting everyone with numbers at the start," said Chief Cabinet Secretary Nobutaka Machimura.

"Rather, as Japan has proposed, we must first build a framework in which all major emitting nations participate.

"Various interests of various nations are being thrown around. So we should first launch negotiations... But I think, if we emphasise numbers too much, we may end up with negative outcomes," he said.

The comment followed an announcement by Australian Prime Minister Kevin Rudd, who said his country would make no firm commitment on cutting greenhouse gas emissions until next year.

Japan's biggest business lobby also warned the government that another set of "irrational" greenhouse gas emission targets like those in the Kyoto Protocol would weaken Japan Inc's competitiveness.

The UN conference on the Indonesian island will attempt to forge a roadmap for a new deal to follow on from the Kyoto Protocol when its first phase ends in 2012.

Delegates from more than 180 nations at the meeting do not have to commit to legally binding targets at this stage as they try to agree a format for negotiations which should be concluded by 2009.

Global warming -- which scientists say is shrinking polar ice caps, causing sea levels to rise and threatening plant and animal species -- is widely seen as one of the most serious long-term threats facing the world today.