Ministers and other representatives from 189 countries and entities are meeting in Montreal this week to debate the shape of the Kyoto Protocol after the UN climate pact's present commitments expire in 2012.

Stalwart Australia broke ranks with the United States to endorse a Canadian proposal for countries to hold talks over the next two years to find ways of curbing greenhouse-gas emissions.

"The reality is that we can only make meaningful global greenhouse gas reductions if effective action is taken by all the major emitting countries," Australian Environment Minister Ian Campbell said.

The conference is taking place under the UN Framework Convention on Climate Change (UNFCCC), the fruit of the 1992 Rio Summit.

Kyoto, its key offshoot, sets targets for industrialised countries to reduce carbon-based gases that act like an invisible blanket, trapping the Sun's heat and driving up the planet's surface temperature.

But the present reduction targets under Kyoto make only a tiny inroad into the problem -- and they only involve a few dozen industrialised countries.

They do not include the United States, which walked away from the accord in 2001 because of the cost of meeting its provisions.

Nor do the targets involve big developing countries such as China, India and Brazil, which are becoming big polluters in their own right.

Treading carefully in a diplomatic minefield, Canada, the conference host, said it wants the UNFCCC "to engage in discussions to explore and analyze long-term cooperative action to address climate change" and with the "widest possible cooperation and participation."

The proposal does not spell out any targets or a timetable or say how the goals would be met, although Canada says the format would have to be flexible.

Even so, the United States voiced its objections to the proposal and defended its argument that smart technology and a voluntary approach, rather than emissions caps and regulations, would fend off climate change.

"It is our belief that progress cannot be made through these formalised discussions," Paula Dobriansky, US Under Secretary for Democracy and Global Affairs told a press conference.

"We believe that the best approach and the best way forward is one that takes into account diversified approaches and differing opinions. One size does not fit all."

Washington's political isolation was highlighted in remarks by other leaders.

European Commissioner for the Environment Stavros Dimas pointedly said the European Union would "continue to talk to our American partners and remind them of their commitments."

"In Gleneagles and at the UN Summit in September, President Bush expressed his commitment to use this meeting here in Montreal to move forward global discussions on future action on climate change," Dimas said.

Canadian Prime Minister Paul Martin too pressed the United States.

"To all those countries that are still reticent, including the United States, I want to say this: We have a global conscience and now is time to listen to that conscience," he said.

"It's time to join with the international community and get down to work, to show leadership, and especially it's the time to take action because only together can we make real and lasting progress."

The Bush administration's approach on tackling carbon emissions was lashed by a group of leading US economists Wednesday.

Twenty-five of them, including three Nobel laureates, called in a letter for the United States to introduce caps and other regulatory policies to spur market incentives that would greatly reduce fuel consumption and carbon pollution.

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