DURBAN: With the heat-trapping carbon at record levels in the atmosphere, UN climate negotiations opened with pressure building to salvage the only treaty limiting greenhouse gas emissions.

The US, Europe and the developing countries laid out diverging positions at the outset, signaling tough talks ahead even as South African President Jacob Zuma called on Monday for national interests to be laid aside ''for a common good and benefit of all humanity.''

As if to illustrate the effects of global warming, a fierce storm on the eve of the talks flooded shack settlements and killed at least five people in the port city hosting the international gathering.

In a statement, municipal officials said the toll could go as high as 10, based on unconfirmed reports.

The climate talks were not affected, though the roof of the sprawling center where the conference was being held was damaged.

Scientists say such unusual weather has become more frequent and will continue to happen more often as the Earth warms, although it is impossible to attribute any individual event to climate change.

The talks face a looming one-year deadline with the expiry next December of the commitment by 37 industrial countries to cut carbon emissions, as required under the Kyoto Protocol.

At issue is whether those countries would accept another period of greater emission reductions.

As the talks opened, Canadian television reported that Ottawa will announce its formal withdraw from the Kyoto accord next month.

Canada, joined by Japan and Russia, said last year it will not accept new commitments, but renouncing the accord would be another setback to the treaty concluded with much fanfare in 1997.

Canadian Environment Minister Peter Kent said he would neither confirm nor deny the report.

''This isn't the day. This is not the time to make an announcement,'' he said.

''Countries are running away from the Kyoto Protocol,'' said Artur Runge-Metzger, the chief negotiator for the European Union.

Canada's withdrawal would not immediately affect the Durban talks, he said.

But doubts about the Kyoto deal is one reason the EU was conditioning its acceptance of new commitments on an agreement in Durban from China, India and other major emitting countries that they will adopt legally binding commitments by 2015.

Developing countries say Kyoto is the only instrument that binds wealthy countries to specific targets.

The protocol was ''the cornerstone of the climate talks and its second commitment period is the essential priority for the success of the Durban conference,'' Chinese delegate Su Wei told the inaugural session.

US chief delegate Jonathan Pershing said the United States, which shunned Kyoto as unfair, would accept legally binding emissions limits in the future as long as all major emitters took on equal legal obligations.

But the US wants to know exactly what such an agreement would contain before it agreed to the principle of a legal treaty which would require the endorsement of two-thirds of the US Senate.

''Putting the form of the action before the substance doesn't make a great deal of sense,'' Pershing told reporters.

Opposition in Congress, which includes outspoken climate skeptics and a Republican majority generally considered climate-unfriendly, has prompted a widespread belief that US negotiators are foot-dragging on emissions issues.

Christiana Figueres, the UN's top climate official, said Kyoto's future is ''the defining issue of this conference.''

She said an extension of Kyoto targets is linked to pledges that developing countries must make to join the fight against climate change.

The task is daunting, she said, and then former President Nelson Mandela said, ''It always seems impossible until it is done.''

In his address opening the conference, Zuma said global warming already is causing suffering and conflict in Africa, from drought in Sudan and Somalia to flooding in South Africa.''For most people in the developing world and Africa, climate change is a matter of life and death,'' said the South African leader.

Zuma said Sudan's drought is partly responsible for tribal wars there, and that drought and famine have driven people from their homes in Somalia.

Floods along the South African coast have cost people their homes and jobs, he said.

''Change and solutions are always possible. In these talks, state parties will need to look beyond their national interests to find a global solution for a common good and benefit of all humanity.''

One of the greatest threats of global warming is to food supplies.

In its first global assessment of the planet's resources, the UN Food and Agriculture Organization estimated that farmers will have to produce 70 per cent more food by 2050 to meet the needs of the world's expected 9 billion-strong population.