By Tim Hirsch
BBC News, Buenos Aires
The US has been defending its decision not to take part in the Kyoto Protocol, just two months before the international agreement to cut greenhouse gases comes into force.
The US says it will do more on climate than many in Europe
Senior US negotiator Harlan Watson attacked the treaty as being politically motivated rather than based on science.
Speaking to reporters at the UN climate change convention in Buenos Aires, he suggested European countries were in no position to lecture the Americans about cutting emissions.
If the State Department official responsible for representing his government at these events likes to be popular, he is clearly in the wrong job.
The chain-smoking diplomat is well used to finding himself the target of attacks from all sides, as the Americans resolutely refuse to contemplate re-joining a process they claim is a threat to economic growth.
Asked by one Brazilian journalist at the news conference here what it was like to be the "bad boy in the movie", Dr Watson replied: "Perhaps there is a perception that it is more important to agree to things rather than taking actions.
"Agreeing to Kyoto does not necessarily mean that you are going to meet those commitments."
The US is keen to emphasise the large amount of government money going into research into technologies such as hydrogen fuel and new forms of nuclear power, which could decrease reliance on fossil fuels such as oil and coal in future.
But Dr Watson admitted that even with proposals to reduce the "carbon intensity" of the US - that is, the amount of carbon dioxide produced for each dollar of the economy - his country is projected to emit about 15% more greenhouse gas in 2012 than in 1990, compared with a reduction of 7% signed up to by the Clinton administration in 1997.
On the treaty itself, the negotiator did not mince his words.
"The Kyoto protocol was a political agreement. It was not based on science."
The Americans get most irritated when they are portrayed as the villains in contrast with European governments which sometimes appear to be wearing a "green halo".
Dr Watson was asked by a German journalist what had gone wrong with the American way of life to make it produce twice the emissions of European economies with similar living standards.
The US says strong economic growth means it uses more fuel
"Nothing went wrong in the US," he said. "We are blessed with economic growth which implies more energy use, which typically implies more emissions.
"I might say, by the way, that your sweeping statement about European reductions does not hold across the board, because there have been substantial increases in a number of countries in Europe."
He may well have had in mind Portugal, whose emissions have risen by 36% since 1990, or Spain, where the growth has been 33%.
The EU is well off course for its target of achieving the cuts set out in Kyoto, but the bloc argues it is tackling the problem through measures such as the Emissions Trading System.
This starts in the New Year and is designed to put economic incentives on cleaner technologies.
The criticism of the US at this conference goes beyond its refusal to ratify Kyoto.
Dr Watson angered many countries and environmental groups by trying to block discussion of the link between climate change and worldwide efforts to improve international disaster relief.
The suspicion of green groups is that the US is fearful of admitting there is a link between industrial emissions and the damage caused by floods, storms and droughts.
After the huge payouts made by the tobacco industry in lawsuits, some believe the courts could well replace conferences like this as the forum for future debates over the causes of global warming.