The nations do not want climate policies to affect economic growth

China, India, South Korea, Japan and Australia and the US account for nearly half of world greenhouse gas emissions.

The US-led initiative would tackle global warming with new technology supplied to countries most in need.

Critics say the new compact undermines Kyoto and is likely to be ineffective because it is non-binding.

'Superior' deal

The pact will allow signed-up countries to set their goals for reducing greenhouse gas emissions individually, with no enforcement mechanism.

The signatories argue it complements, rather than weakens, the 1997 Kyoto agreement, which imposes targets on industrialised countries to cut their emissions.

Australian Prime Minister John Howard said: "The fairness and effectiveness of this proposal will be superior to the Kyoto protocol.

"It demonstrates the very strong commitment of Australia to reducing greenhouse gas emissions, according to an understanding that it's fair in Australia and not something that will destroy Australian jobs and unfairly penalise Australian industries."

US Deputy Secretary of State Robert Zoellick agreed the six nations "view this as a complement, not an alternative" to Kyoto.

Both the US and Australia have refused to ratify Kyoto, which came into effect earlier this year, partly, they say, because big developing countries like India and China escape emissions limits.

'Win-win'

They have also made clear their concern that climate change should only be addressed without harming development or economic growth.

Australian Foreign Minister Alexander Downer told BBC Radio 4's Today programme: "Our view is you really need to focus on technological change to solve the climate change problem... and you do have to involve the major developing countries, which are very substantial emitters."

A Chinese spokesman called the pact a "win-win solution" for developing countries.

A deal on climate change that doesn't limit pollution is the same as a peace plan that allows guns to be fired

Worldwide Fund for Nature

The UK government's chief scientific adviser, Sir David King, told the BBC's Today radio programme he doubted the new deal could work without setting caps on emissions.

But, he added, the surprise announcement should be seen as a sign of progress on climate change.

Environmental campaigners have criticised the new pact as ineffectual and serving the interests of industrialised nations.

The Geneva-based Worldwide Fund for Nature (WWF) said: "A deal on climate change that doesn't limit pollution is the same as a peace plan that allows guns to be fired."

Bob Brown, leader of Australia's opposition Green party, dismissed the agreement as a "coal pact" involving four of the world's largest coal producers - China, the US, India and Australia.

The new group's first summit will be held in Adelaide, Australia, in November.