The latest round of UN climate talks opens in Barcelona on Monday with major divisions remaining between countries.
The week's session is the final chance for negotiators to hammer out a text before December's Copenhagen summit
In recent weeks, UN officials have declared there is no chance of agreeing all elements of a new legally-binding UN treaty before the end of the year.
But they are still hoping to agree major elements of a treaty to supplant the Kyoto Protocol.
The main areas where big divisions remain include:
the extent to which developed countries should cut their greenhouse gas emissions
how much money rich nations should contribute to help poorer ones reduce their emissions and adapt to climate impacts
how far developing countries will go in constraining the rise in their greenhouse gas emissions
UN Secretary-General Ban Ki-moon dampened expectations further last week by appearing to suggest that nothing legally binding might be possible in Copenhagen.
"If we can agree on four political elements, then that could be a hallmark of success on climate change," he said.
But the Danish hosts and other governments, including the UK, remain determined to secure something with legally-binding elements.
For the UK, it must contain numbers on mitigation targets and adaptation funds; and ministers have said they will not sign something they consider to be too weak.
"I think we should not sign up to a deal that is inadequate," Climate Secretary Ed Miliband said last week.
Gaps to bridge
Pledges by developed countries to cut emissions by 2020 (from 1990 levels) fall far short of the 40% that developing countries are demanding.
The US may not be in a position to pledge anything at all, with domestic legislation yet to pass through the Senate.
The EU said last week it would contribute its "fair share" of the $100bn euros ($148bn; £90bn) per year that it calculates the developing world will need by 2020 in order to curb their emissions and protect their societies and economies from climate impacts.
But it stopped short of naming an exact figure for its contribution.
Studies by UN agencies suggest more than that is needed, and that funding on this scale should begin next year, rather than in 10 years' time.
A number of developing countries, notably Indonesia, have recently pledged to reduce the rate at which their emissions will rise; but the biggest of all - China - has yet to announce by how much.
Even the legal form of a new treaty remains to be decided, with a number of developing countries insisting that it must be an extension to the Kyoto Protocol, and industrialised governments equally insistant that it must be a completely new agreement - not least because the US Senate will not ratify the Kyoto Protocol.
Negotiators will begin work with a set of "non-papers" - elements of a possible treaty that do not carry the weight of a formal draft.
The chairman of the main set of talks, Michael Zammit Cutajar, has advised negotiators to concentrate on the "critical issues... that are central to the task", with details that could bog the discussions down left to one side.
