CANCUN (AFP) - World climate talks in Cancun were on Sunday entering their final stretch beset by fears of a repeat of the failures that nearly wrecked the December 2009 Copenhagen summit.

Environment ministers began arriving in the Mexican resort city at the weekend to find themselves plunged into a mood soured by a row over the Kyoto Protocol and a logjam of inter-connected, unresolved issues.

After more talks among senior officials, the ministers on Tuesday get down to a four-day haggle, due to climax on Friday.

The outcome of the UN Framework Convention on Climate Change (UNFCCC) gathering is unclear, despite 12 days of meetings and a low-ambition goal, say delegates.

"We're starting to have positions that are a bit stronger and a bit more radical," said France's climate negotiator Brice Lalonde, calling for a "spirit of compromise."

Wendel Trio, the international climate policy director for environmental group Greenpeace, said that so far countries had only spelled out their "most extreme positions."

"We need ministers to decide on a Third Way -- a solution that builds momentum toward sealing a strong climate deal next year," he said.

The 194 UNFCCC parties are under pressure to restore faith in the UN's bid to slow and then stop the juggernaut of climate change.

The hope is that Cancun will prepare the ground for curbs on man-made greenhouse gases and give the go-ahead to a fund to help channel hundreds of billions of dollars in aid towards poor, vulnerable countries.

This low-key approach contrasts with the vision of Copenhagen, where dreams of an overarching deal blessed by world leaders turned into a nightmare of squabbles and nit-picking.

Memories of that trauma have been renewed in Cancun.

Negotiators face the task of securing consensus in hugely detailed issues ranging from verifying emissions pledges and preventing deforestation to clean-technology transfer and nitty-gritty details about the future "Green Fund."

Worse, an outcome in this negotiating arena is imperilled by a row in the conference's other forum, covering the future of the Kyoto Protocol.

"There are two pillars in this system," Chinese head negotiator Su Wei told AFP on Saturday.

"If one pillar is got rid of, you can imagine how the general architecture would look like and there will be certainly a collapse."

The Kyoto Protocol's commitments run out at the end of 2012 and Japan has bluntly refused calls to extend it tentatively. The treaty only requires wealthy nations to cut emissions, but the United States rejected it in 2001.

Japan says it is pointless, and unfair, for industrial powers to bind themselves to tough, legally binding constraints when huge polluters -- China and the United States, especially -- have only voluntary pledges.

Japanese negotiator Hideki Minamikawa called for "a new framework in which all those countries including all the major emitters can work together to continue our essential combat against climate change."

Delegates say that Canada and Russia could be tempted to join the exodus, weakening or even destroying a treaty seen by developing countries as a sacred text. However, Australia said it would accept a second Kyoto period.

The Cancun meeting caps a year in which climate change has been all but driven off the political map by the near-fiasco in Copenhagen and fixation with economic crisis.

Scientists, though, say the peril is worse than ever, and stringent reductions are needed on carbon pollution within the next 40 years to prevent potentially catastrophic damage to the climate system.

Emissions of carbon dioxide, the principal greenhouse gas, scaled new peaks in 2009, and 2010 is on course for becoming one of the three warmest years on recorded and the decade 2001-2010 the hottest ever, according to new research.

By 2030, climate change could be claiming nearly a million lives a year and inflicting costs of 157 billion dollars annually, a study issued at the conference said Thursday.

Poor countries would suffer most in terms of lives lost, while the United States would face the biggest economic bill.