The European Union called on developing countries Tuesday to take immediate steps to reduce greenhouse gases, saying they must stop blaming richer nations for their own failure to act.

Policymakers from around the world are meeting with scientists in Bangkok this week to adopt a blueprint for preventing global warming from having catastrophic effects.

But the guidelines proposed by the Intergovernmental Panel on Climate Change, the United Nations network of 2,000 scientists that has produced two landmark reports on global warming this year, are drawing criticism from the United States and China.

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In comments submitted ahead of the meeting, the U.S. and China say the proposed cap on greenhouse gas levels is too low and reaching the target would be too expensive.

The two countries are expected to attempt to insert language into the final report that would weaken the conclusion that quick action can stabilize greenhouse gas levels.

In its draft report, the panel says that by rapidly embracing energy efficiency and reducing its reliance on fossil fuels, the world may manage to hold the temperature rise to 3.6 degrees Fahrenheit, beyond which the planet may become inhospitable to life.

Even an increase of 3.6 degrees could mean water shortages for as many as 2 billion people by 2050 and extinction for 20 percent to 30 percent of the world's species, the IPCC said.

Tom van Ierland, a climate change expert with the European Union, said cooperation from developing countries is essential to the goal of keeping temperatures from climbing more than 3.6 degrees, or 2 degrees Celsius.

The EU is providing tens of millions of dollars in funding for energy efficiency projects in developing countries and supports policies "they themselves can implement to increase their energy efficiency and energy security," he said.

"We need to ensure that in coming years the growth of emissions in developing countries is reduced and eventually capped to be in line with our 2 degree objective," he told reporters.

While he didn't single out any countries, Van Ierland also called on governments to stop using the inaction of some of the world's biggest polluters as an excuse for not implementing their own policies to cut greenhouse gases.

China, the world's biggest emitter of greenhouse gases after the United States, has said richer countries are responsible for global warming and should take the lead in cleaning up the problem.

The United States and Australia have refused to sign the Kyoto Protocol, a U.N. treaty on climate change, partly over objections that China and India are not held to carbon pollution reduction targets.

Van Ierland said it was "sad" some countries were resorting to "this rhetoric" when action was in order.

For it to be considered valid by the United Nations, the IPCC draft must be unanimously approved by the 120-plus governments that participate, and all changes must be approved by the scientists.

While the report does not mandate action like the Kyoto Protocol, it could influence negotiations over future climate pacts.

Harlan Watson, the head of the American delegation, said in an e-mail that the U.S. goal is to produce a report that is "useful to the policy community" and is "supported by scientific and economic data."

In its first report this year, the scientific panel expressed its greatest confidence yet that global warming is being caused largely by the accumulation of carbon dioxide and other heat-trapping gases in the atmosphere.

The second predicted catastrophic consequences unless man stops burning coal, oil and other fossil fuels that produce greenhouse gases.