After two weeks of negotiating talks went through the night Thursday, with delegates struggling to keep Durban from becoming the graveyard of the 1997 Kyoto Protocol on global warming.
"If there is no further movement from what I have seen until four o'clock this morning, then I must say I don't think that there will be a deal in Durban," said Connie Hedegaard, the European commissioner for climate action.
The proposed package would see the EU extend its commitments to reduce greenhouse gas emissions under the 1997 Kyoto Protocol, but only if all other countries agree to negotiate a new treaty with legally binding obligations for everyone, not just the wealthy Kyoto group.
The EU has said it will not renew its emissions reduction pledges, which expire in one year, without agreement to begin work on a treaty to replace the Kyoto accord that would compel all countries to control their emissions, including the US and China which are the world's two largest polluters.
The US never ratified the protocol, though it has made voluntary efforts to reduce emissions.
The Europeans won critical support late on Thursday from an alliance of small islands and the world's poorest countries - about 120 nations altogether - for its proposal to start negotiations now on a deal to take effect in 2018 or possibly after 2020.
Brazil and SA also said they would accept binding emissions limits under a new agreement. The two countries are among the countries in the so-called developing world that emit the most greenhouse gases.
Ministers or senior negotiators from 28 countries then worked late through the night to try to bring the US, China and India on board.
Hedegaard said the three countries are still not on board and could scuttle the deal.
Both China and the US have said they would be amenable to the EU proposal to negotiate a post-2020 agreement, but each attached riders that appeared to hobble prospects for unanimous acceptance.
The US, whose Congress is generally seen as hostile on the climate issue, is concerned about conceding any competitive business advantage to China. Beijing, too, is resisting the notion that it has become a developed country on par with the US or Europe, saying it still has hundreds of millions of impoverished people.
Rich countries are legally bound to reduce carbon emissions while developing countries take voluntary actions.