"We think it's a very valuable report. The conclusions are significant," he said, adding that "the US was an important participant in the development of this report."

US Commerce Secretary Carlos Gutierrez said Friday he was proud of the National Oceanic and Atmospheric Administration, which his department oversees, for being a "leader in expanding our knowledge of our changing climate and our changing world.

"I'm proud that NOAA's world-class research -- particularly our cutting-edge modeling of climate change -- provided a firm foundation for the work of this international panel," said Gutierrez, who is in Mexico for meetings with President Felipe Calderon and other top officials.

In their starkest warning yet about global warming, UN scientists said fossil fuel pollution would raise temperatures this century, worsen floods, droughts and hurricanes, melt polar sea ice and damage the climate system for 1,000 years to come.

The keenly anticipated report from the Intergovernmental Panel on Climate Change (IPCC), its first assessment in six years, dealt a crippling blow to the shrinking body of opinion that claims higher temperatures in past decades have been driven by natural, not man-made, causes.

The US Department of Energy said in a statement that the report confirms what President George W. Bush has said about "the nature of climate change, and it reaffirms the need for continued US leadership in addressing global climate issues."

Energy Secretary Samuel Bodman said the administration welcomed the report, "which was developed through thousands of hours of research by leading US and international scientists and informed by significant US investments in advancing climate science research.

"Climate change is a global challenge that requires global solutions. Through President Bush's leadership, the US government is taking action to curb the growth of greenhouse gas emissions and encouraging the development and deployment of clean energy technologies here in the United States and across the globe."

Earlier this month in his State of the Union address, Bush set out goals to curb gas guzzling by vehicles in the United States, which alone accounts for nearly a quarter of global carbon pollution.

He said the United States should cut its use of oil by 20 percent over the next decade by encouraging the use of renewable and alternative fuels, and overhauling fuel efficiency standards for cars.

But the US president has resisted international calls for binding caps on carbon gas emissions, and in 2001 he abandoned the Kyoto Protocol for curbing greenhouse gas emissions, saying its limits were unfair and too costly for the US economy.

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