Agreement is needed to send a clear signal to developing countries that rich nations are willing to shoulder the burden on climate change, a problem they created by burning the fossil fuels that drove their prosperity.

"It's not easy to get all industrialised countries onboard," German Environment Minister Sigmar Gabriel said at the 12-day talks.

Sources singled out Russia, which has suggested that non-industrialised countries be allowed to set "voluntary targets" on cutting emissions.

This would give those countries access to Kyoto's lucrative market mechanisms, which at present are reserved for industrialised nations.

Delegates said the idea seemed to be pitched for Moscow's ally, Belarus, which would have plenty of excess emissions to sell on the global carbon market.

Environment ministers began meeting in Nairobi on Wednesday, and many have used the podium to issue dark warnings of the looming havoc of climate change.

They have until late Friday to match commitment with rhetoric, to show that the next round of pollution controls after Kyoto's current pledging session ends in 2012 will be tough enough to meet the challenge.

In its present format, Kyoto will not even dent global emissions of carbon gases -- the by-product of burning fossil fuels that capture heat from the sun and drive dangerous climate change.

One of Kyoto's flaws is that it does not include the world's biggest polluter, the United States, which by itself accounts for a quarter of global output of man-made emissions.

After signing up to Kyoto as a framework treaty and then largely determining its complex machinery, the United States, under President George W. Bush, walked away from the accord in 2001.

Nor does Kyoto include big developing countries such as China and India in targeted emissions cuts which at present are only shoulded by industrialised countries.

These countries are not historically responsible for today's problems but their surging economic growth and voracious burning of oil, gas and coal are making them huge carbon polluters in their own right.

Negotiations for Kyoto's second commitment period, running from 2013 to 2017, will start in earnest next year.

While some countries want the deal to be wrapped by the end of 2008, most expect the conclusion to come at the end of 2009, given the vast complexities -- especially the key question of developing countries' commitments.

This has major implications for the United States, for in essence it would sideline the US from shaping the 2013-2017 commitment period -- a process that potentially carries vast rewards in carbon trading and investment.

"If we accept the premise that Bush is not going to change his stripes, then we are waiting for a new president" for any US return to Kyoto, said Greenpeace campaigner Steve Sawyer.

As every new president takes at least half a year to settle in, make new appointments and take the measure of Congress, it would be impossible for the United States in 2009 to ratify Kyoto in time to join the negotiations for 2013-2017 round, Sawyer observed.

"The timing works just about right for the US to come in for the formal negotiations on (...) the third commitment period, covering 2018 to 2022," he said.

On Wednesday, three leading Democratic senators said that next year they would push for laws setting mandatory limits on greenhouse gases and urged Bush to work with the international community to forge an "equitable" global agreement on climate change.

Senators Barbara Boxer, Jeff Bingaman and Joseph Lieberman are set to head key committees on global warming when Democrats take over Congress in January, following last week's crushing electoral defeat for Bush's Republicans.

Related Links
United Nations Framework Convention on Climate Change
Learn about Climate Science at TerraDaily.com