These expensive scenarios, he said, would bring cuts in world gross domestic product of as much as 3 percent.

"Well, that would of course cause global recession, so that is something that we probably want to avoid," Connaughton said in a telephone briefing after the release in Bangkok of the report by the Intergovernmental Panel on Climate Change.

One example of a currently prohibitively expensive fix would be to produce power from coal with no emissions, he said.

The latest document -- the third in a series -- offers a range of scenarios, pegged to different so-called stabilization levels of greenhouse gases in the atmosphere. Measured in parts per million, the current level is about 430.

One version that would put the stabilization level of greenhouse gases in 2030 between 445 and 535 parts per million estimates the negative impact on gross domestic product at less than 3 percent over more than two decades. The annual impact was estimated at less than 0.12 percent.

Other scenarios have more modest goals for 2030, with higher stabilization rates of greenhouse gases and less impact on the global economy. Connaughton noted these strategies have "relatively little economic cost and ... potentially significant economic and health benefits."

These include increased energy efficiency and air pollution controls, he said.

WINDOW OF OPPORTUNITY

Overall, he and other Bush administration officials praised the report as offering a range of options, including some the United States is already pursuing, including increased energy efficiency, renewable fuels and new technologies.

The United States is the world's biggest emitter of greenhouse gases. Environmentalists, corporate groups and some US lawmakers have been pushing for a federal law to cap carbon emissions, but the White House has urged voluntary limits.

The Bangkok report stressed the need for immediate action, a cause taken up by US environmental groups.

"We have a window of opportunity, but it won't stay open forever," said Steve Cochran, national climate campaign director at Environmental Defense. "Anyone pushing for delay is pushing for higher costs and longer odds."

"It's especially troubling that the Bush administration was seeking last-minute changes to play down the report's conclusion that quick, affordable action can limit the worst effects of global warming," Larry Schweiger, president of the National Wildlife Federation, said in a statement.

Rep. Ed Markey, a Massachusetts Democrat who heads the new US House of Representatives global warming committee, said in an e-mail: "There is no silver bullet to stop global warming."