Bush administration officials and members of the Republican-led Congress are in general uncomfortable when asked to discuss global warming.
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They know that US policy is at odds with most scientific experts on the issue, ever since President Bush pulled the US out of the Kyoto process soon after taking office in 2001.
The US position is flying in the face of a broad consensus of world opinion that urgent collective action is required to reduce industrial emissions that add to global warming.
President Bush and Congress also know that to support legislation obliging US industrial plants to reduce emissions - as Kyoto demands - would be a vote loser, because it would mean cutting production, increasing unemployment and raising energy bills.
The most recent attempt by Kyoto process supporters to introduce a Senate bill failed in October.
The draft, called the Climate Stewardship Bill, was dubbed "Kyoto Lite" by its detractors.
It was co-sponsored across party lines by Democrat Joe Liebermann - one of next year's presidential election hopefuls - and Republican John McCain.
Critics of the bill argued that it would have reduced US GDP by $106 billion and raised energy costs by at least 30%.
Among those who regularly speak up vociferously against global warming legislation is James Inhofe, the Republican chairman of the Senate environment committee.
Mr Inhofe is representing the US position at the UN conference on climate change in Milan this week.
He has gone so far as to describe the whole concept of industrial global warming as a hoax perpetrated by politically mischievous environmentalists.
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He quotes findings of a study by Dr Willie Soon and Dr Sallie Baliunas, of the Harvard-Smithsonian Centre for Astrophysics, that determined the 20th century was neither the warmest, nor the century with the most extreme weather within the past millennium.
They conclude global warming is a natural phenomenon on which modern-day industrial emissions have no significant impact.
It is a view that fits neatly with the majority view in Congress that US industry need do nothing at all about global warming.
Some US opponents to Kyoto also argue that the UN-backed conference process is little more than a cover for shifting political power away from the US.
As evidence, opponents of Kyoto quote French President Jacques Chirac - something of a bogeyman figure among Republican conservatives - who they say once described the Kyoto treaty as a key step on the path to "global governance".