Annan -- whose valedictory speech to environment ministers coincided with a watershed in the Iraq war and the row over Iran's nuclear programme -- pointedly said leaders should give global warming the same priority they gave to violent conflicts and the spread of weapons of mass destruction.

The UN secretary-general said the Kyoto Protocol, while crucial, was "far too small" a step for tackling the carbon pollution which drives global warming.

"As we consider how to go further still, there remains a frightening lack of leadership," Annan sombrely warned.

He said climate change imperilled agriculture through drought, threatened coastal cities through rising sea levels and opened the door to billion-dollar weather calamities and mosquito-borne epidemics.

"Climate change is also a threat to peace and security," Annan warned.

"Changing patterns of rainfall, for example, can heighten competition for resources, setting in motion potentially destabilising tensions and migrations, especially in fragile states or volatile regions.

"There is evidence that some of this is already occurring; more could well be in the offing."

Annan declared: "The message is clear. Global climate change must take its place alongside those threats -- conflict, poverty, the proliferation of deadly weapons -- that have traditionally monopolised first-order political attention."

But Annan's appeal for a fresh tack was followed by signs from key actors in the climate-change debate that they were happy to camp on familiar positions.

The United States, the world's biggest carbon polluter, set out a stall laden with familiar policies that reject Kyoto's mandatory and multilateral format in favour of a voluntary approach, bilateral partnerships and technological innovation.

Senior US delegate Paula Dobriansky, who is undersecretary of state for democracy and global affairs, rejected Annan's criticism that there was no leadership on climate change.

"We think the United States has been leading with its groundbreaking initiatives," she told journalists.

Ministers or their stand-ins at the 189-nation meeting of the UN Framework Convention on Climate Change (UNFCCC) are under pressure to spell out by Friday their commitments for deepening cuts in greenhouse-gas emissions.

The spotlight is being placed on Brazil, China and India -- big-population developing countries whose carbon pollution has surged in line with their economic growth.

According to one estimate, China may overtake the United States as the No. 1 polluter by the end of the decade, thanks to its voracious burning of coal.

The big question is whether these countries will join rich nations in making binding curbs in their emissions when negotiations start next year to reshape the UNFCCC's Kyoto Protocol after it expires in 2012.

The absence from the big developing countries in the current targeted pledges is cited by the United States and Australia as a reason why they have refused to ratify Kyoto.

Australian Environment Minister Ian Campbell called for "a new Kyoto" that would cover "all the major economies."

But senior Chinese delegate Jiang Weixin rejected such thinking.

China was willing to take part in talks on long-term emissions cuts, he said.

But the dialogue could not usurp the UNFCCC, and it should be "neither a negotiation process, nor an attempt to set up emission reduction limitation targets for the development countries," Jiang said.

Jiang said the onus in the post-2012 negotiations fell on industrialised countries, which first had to show what cuts they were willing to make.

As expected, countries of the European Union loudly championed Kyoto but skirted the thorny issue of whether they wanted big developing countries to join industrialised nations in signing up to binding emissions commitments beyond 2012.

In a speech read to the conference, French President Jacques Chirac called for "an effective and strengthened multilateral regime" post-2012 that would include "all industrialised countries... and better associate emerging countries, whose emissions are growing swiftly."

British Environment Secretary David Miliband spoke of a "global framework for emissions reductions, driven by the science, fair in its burdens, and urgent in its delivery."

Greenhouse gases trap the Sun's heat instead of letting it radiate out into space.

As a result, Earth's atmospheric temperature is rising, and many scientists are convinced this is already starting to affect the climate system.

Experts are demanding swingeing cuts in the pollution to avoid prolonged droughts and floods or melting of the Antarctic ice sheet that could unleash an alarming rise in sea levels.

The Nairobi conference, which began on November 6, yielded its first significant progress on Tuesday with deals on technical aspects of Kyoto's complex machinery.

Financial experts on Tuesday warned climate change could so amplify the effect of weather disasters that droughts, storm surges and other natural catastrophes could cost as much as a thousand billion dollars in a single year by 2040.

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