"In the United States there is growing interest and growing concern but no chance of joining Kyoto," he told Reuters by telephone. "The word is radioactive."

Clinton, a Democrat, did not present Kyoto to the Republican dominated Senate in 1998 knowing it would be defeated.

Clinton's Republican successor US President George W. Bush turned his back on the treaty -- the only legally binding global accord on climate change -- arguing that it would be economic suicide to sign up to Kyoto while allowing major developing nations like China and India to be exempt.

Kyoto obliges 35 developed nations to cut greenhouse gases by at least 5 percent below 1990 levels by 2008-12. Governments are now wrangling over how to extend the protocol beyond 2012.

Bush is entering the last two years of his administration, but is not expected to change course on the environment.

Mid-term elections last month gave Democrats control of Congress by a tiny margin, reawakening speculation of a shift towards accepting Kyoto-style caps.

But for Eizenstat, a former US deputy treasury secretary and under secretary of commerce for international trade, the numbers simply do not add up because it needs a two-thirds majority to get laws through -- and that looks unlikely given most Republicans' ideological hatred of Kyoto.

"With the changeover in Congress we really do have the potential for greater interest but not really legislation. It hasn't changed the dynamic," he added.

And that is despite the introduction in California by Republican governor Arnold Schwarzenegger of tough climate laws, and a carbon emissions trading deal between seven other states.

"California has a formal Kyoto-type emissions law. It is very important to see what they do on emissions trading," Eizenstat said. "The whole history of environmental laws is that they start in California and head east."

There is a chance the Senate might agree a less strict goal.

It has voted down calls to set mandatory caps on emissions at 2000 levels -- an easier target than Kyoto. But backers of that bill say they will try again in 2007.

However, a law passed in 1997 barred the US from making international commitments on carbon emission cuts unless developing countries did likewise -- and that, according to Eizenstat, cuts across party lines.

"It would be very difficult to get the US into some sort of Kyoto commitment without China," he said. "Unless China undergoes a metamorphosis you would have real difficulty."

Talks to extend Kyoto have made little headway -- due partly to US meddling and partly to uncertainty over the intentions of China, which builds one coal-fired power plant a week.

Most scientists agree that temperatures will rise by between two and six degrees Celsius this century due mainly to carbon emissions from burning fossil fuels for power and transport, putting millions of lives at risk from floods and famines.

Former World Bank chief economist Nicholas Stern said in October that urgent action on global warming was vital, and that delay would multiply the cost 20 times.

Eizenstat said one possibility was that the United States would at some stage be forced by the spreading patchwork of business and state actions to bring in federal emissions laws.