Four days before the high-stakes climate meeting opens in the Danish capital, President Barack Obama and his allies are trying to show US commitment to a global deal even though key legislation has yet to clear through Congress.

Senator John Kerry invited executives of major companies to the US Capitol to provide ammunition for his and Obama's argument that US restrictions on carbon emissions blamed for global warming would generate a new green economy.

"If you look at China in particular, despite how much of the US wants to portray it sometimes, they are being very aggresive in developing energy efficient products," said David M. Cote, chairman and CEO of US conglomerate Honeywell.

"We're lagging behind in that job creation," Cote said.

Preston Chiaro, group executive for technology and innovation at Rio Tinto, said the Anglo-Australian mining giant was creating 1,500 jobs in California by building a carbon capture plant, which will have 100 permanent jobs once completed.

"We think that the lack of certainty around climate legislation is actually hindering investment," Chiaro said. "This new technology will open the door for the future of coal and that's why we support it."

Kerry's push on climate change also enjoyed a boost from Senator Lindsey Graham, a prominent member of the rival Republican Party who has broken ranks to work on a bill.

"You'll never convince me that America cannot have the cleanest air and the purest water of any place on the planet," Graham said.

"If Congress does not act soon, the world will leave us behind," he said.

But other Republicans spoke out sharply against climate legislation, saying that plans by Obama and House Speaker Nancy Pelosi to head to Copenhagen showed they were out of touch with US voters concerned about the economy.

"The president and the speaker have far more pressing problems to worry about here at home -- namely stopping runaway spending, getting our fiscal house back in order and working on some common-sense solutions that get Americans back to work," said Eric Cantor, the number two Republican in the House of Representatives where a climate bill squeaked through in June.

Climate change skeptics also seized on leaked emails by British scientist Phil Jones of the University of East Anglia which called into question the basis for studies that the planet is heating up.

The emails offered "increasing evidence that scientific fascism is going on," said Republican Representative James Sensenbrenner.

But Senator Joe Lieberman, an independent who usually votes with Obama's Democrats, told reporters that lawmakers had other studies showing climate change was real and predicted legislation would pass in the new year.

Obama plans to tell Copenhagen that the United States will cut carbon emissions by about 17 percent by 2050 off 2005 levels, in line with legislation in Congress although less ambitious than what UN scientists recommend.

India on Thursday followed China's lead in announcing it would commit to hard numbers on reducing the intensity of its carbon output.

The United States had demanded that developing countries take action as part of the next international treaty. The Kyoto Protocol, whose obligations run out in 2012, required emission cuts only from wealthy nations.

Nine Democratic senators, some from heavy-industry states, wrote to Obama calling for him to insist on a "global response" on climate change.

"Poorly designed climate policies could jeopardize US national interests by imposing burdens on US consumers, companies and workers without solving the climate challenge," they wrote.

The letter was signed by senators Mark Begich, Sherrod Brown, Kay Hagan, Tim Johnson, Amy Klobuchar, Carl Levin, Claire McCaskill, Arlen Specter and Debbie Stabenow.

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