Mr Rudd described as horse-trading yesterday the process in Bali in which the Australian delegation has voiced support for a 2020 target for cutting emissions in the range of 25 to 40 per cent.

He insisted he would not set a 2020 target until next year, when a report by economist Ross Garnaut into emissions trading and the impact of interim targets will be submitted.

The Bali conference is seeking to establish a road map for two years of talks towards a post-Kyoto greenhouse treaty.

"It will be a negotiation and negotiations involve horse-trading. People here know a bit about what horse-trading means," Mr Rudd said. "It means that you sit down with other governments and work out what's necessary for the planet, what's necessary for everyone to contribute, including Australia. Therefore, frankly, it would be irresponsible from that point of view to go out there and put a number on the table straight away."

Mr Rudd also said he had outlined to Chinese Prime Minister Wen Jiabao this week his intentions of playing a leadership role in climate talks.

"In my discussions with the Chinese Prime Minister in the last few days, and with others, I've indicated that we'll be doing whatever we can to try and bridge the gap between developed and developing countries."

United Nations Framework Convention on Climate Change executive secretary Yvo de Boer said despite what had been said, Australia had not formally committed to a 2020 goal.

"I haven't heard if they are willing to do that, but I have heard Prime Minister Rudd say that he wants ambitious targets for Australia ... in the future period," he said in Bali.

Mr de Boer said Australia would not be too late, as legally binding targets would come at the end of the two-year negotiating period.

"Otherwise, it's a bit like going on a shopping trip and not knowing how much money you have got in your pocket."

Meanwhile, Australia has ranked third last in a new study that assessed how much or how little 56 countries have done to protect the climate.

The only nations that performed worse were the United States, which finished second last, and Saudi Arabia, in last place.

The environmental group Germanwatch took aim at Australia's "very poor" performance in its latest Climate Change Performance Index, having slipped to 54th position from 47th last year.

The latest index, published yesterday, evaluates and compares the climate protection performance of the 56 countries that are responsible for 90 per cent of energy-related carbon dioxide emissions.

It says that in large parts of the world, including Australia, the United States and Canada, "appropriate climate protection has not been exercised yet". AAP