BANGKOK, Thailand - The United States and China want to change a draft report written by hundreds of the world's leading climate change researchers to downplay its conclusion that quick action can limit the expected catastrophic effects of global warming.

Among other things, the two countries cast doubt on claims by international researchers that immediate moves could stabilize greenhouse gas levels and limit the temperature rise to two degrees Celsius.

Criticism of the draft by Washington and Beijing were among dozens of comments and proposals submitted by 119 governments ahead of this week's Intergovernmental Panel on Climate Change meeting in Thailand.

The submissions, viewed by The Associated Press on Monday, provided a preview of what delegates expect will be a fight for much of the week to preserve the key conclusions in the draft IPCC report.

The report concludes that greenhouse gas emissions can be cut below current levels if the world shifts away from fuels like coal, invests in energy efficiency, reforms the agriculture sector, and works to halt deforestation.

The Bush administration has rejected the Kyoto Protocol's mandatory emissions cuts, contending they would slow U.S. economic growth. China, which was exempted from the 1997 pact because it is classed as a developing country but is poised to become the world's leading gas emitter, has called on the U.S. and other developing countries to take the lead before it acts.

Canada aims to reduce the current level of greenhouse gas emissions by 20 per cent from 2006 levels by 2020, according to an initiative released by the Conservative government last week. But the government acknowledged it would not meet its obligations under Kyoto, which Ottawa signed in 1997.  Ottawa has not officially withdrawn from the treaty but the Kyoto targets have been abandoned. Kyoto requires 35 industrialized countries to cut greenhouse-gas emissions by five per cent below 1990 levels by 2012. Canada's emissions are currently 30 per cent above 1990 levels.

Two previous IPCC reports this year painted a dire picture of a future in which unabated greenhouse gas emissions could drive global temperatures up as much as six degrees Celsius by 2100. Even a two-degree rise could subject up to two billion people to water shortages by 2050, and threaten extinction for 20 to 30 per cent of the world's species, the IPCC said.

The report being debated this week in Bangkok stresses the world must quickly embrace a basket of technological options -- already available and being developed -- to limit the temperature rise to two degrees C. More than 200 delegates will examine the IPCC report and recommend changes before it is finalized.

The U.S. wants clauses inserted saying the cost of current available technologies to reduce emissions "could be unacceptably high,'' and calling for a greater emphasis on "advanced technologies,'' many of which are aimed at extending the use of coal.

The United States and China also criticized the economics in the report, which concludes that stabilizing the greenhouse gases to limit the temperature rise to two degrees would cost less than three per cent of the global gross domestic product over two decades.

A British government report last year predicted that the damage from unabated climate change might cost the global economy between five and 20 per cent of GDP every year.

The Chinese delegation, which could not be immediately reached for comment, joined the U.S. in trying to delete language saying the potential to reduce global warming was "significant,'' and questioning the affordability of taking action.

The United States says it has "provided billions of dollars'' in incentives to increase the use of nuclear energy, renewables, and clean-coal technologies. It has set a goal of reducing greenhouse gas emissions by 18 per cent over the next five years, said Harlan Watson, head of the U.S. delegation, in an e-mail.

"Our goal throughout the IPCC process is for the reports to best reflect the latest state of knowledge on addressing global climate change,'' Watson said.

Rajendra Pachauri, chairman of the climate change panel, wouldn't address the U.S. concerns directly. But he said every country would have a chance to express its views, and ultimately "a balanced assessment'' of the science will prevail.

"The science certainly provides a lot of compelling reasons for action,'' Pachauri said.

The IPCC was established under the auspices of the World Meteorological Organization and the United Nations Environmental Program to provide regular assessments to policy makers on scientific, socio-economic and technical aspects of climate change.