Lumumba Stanislaus Di-Aping, Sudan's UN ambassador, who represents developing nations at the climate talks, speaks about a contentious Danish draft proposal on Tuesday. (Jens Norgaard Larsen/Scanpix Denmark/Reuters)

Negotiators at the Copenhagen climate summit are trying to bridge a gap between developing countries and wealthy nations over who should shoulder the cost burden.

On Tuesday, African activists stormed out of the meeting room and staged a protest after a draft proposal from Denmark was leaked. The Danish document suggested that rich nations could cut fewer emissions while the developing world should face tougher limits on greenhouse gases.

Sudan's UN ambassador, Lumumba Stanislaus Di-Aping, who is also the chair of the G-77 and China bloc of developing countries, claimed the Danish proposal puts an unfair burden on poor countries.

"We will not sign an inequitable deal," he said. "We will not accept a deal that condemns 80 per cent of world population to further suffering and injustice."

The United Nations and Denmark played down the leaked document Wednesday. Danish officials said it was simply one of many "working" papers making the rounds at the summit. The chief negotiator for the European Commission said it has no validity unless it's presented formally.

Rich-poor divide

The clash underscores the divide between rich and poor, as the summit tries to reach an agreement on how to reduce emissions globally.

The Pacific island nation of Tuvalu, which would be among the first victims of rising seas, proposed amending the UN climate treaty to require nations to keep the rise in global temperatures to less than 1.5 degrees Celsius above pre-industrial levels.

Industrialized countries have set a rise of two degrees as a target.

"Our future rests on the outcome of this meeting," said Tuvalu delegate Ian Fry.

The Danish conference president, Connie Hedegaard, did not advance the proposal after many countries objected.

U.S. climate envoy Todd Stern said getting an agreement that satisfies both rich and poor nations would not be easy.

"But I think an agreement is there to be had, if we do this right," he added.

With files from The Associated Press