The five-day session is the last formal parlay before heads of states and ministers gather in the French capital to seal a deal to beat back the threat of global warming and help poor nations cope with its impacts.
Today will be the first opportunity for rank-and-file negotiators to weigh in on a new draft whittled down from 80 pages to 20 by two senior diplomats -- one from Algeria, the other from the United States -- leading the process.
Many countries are likely to insist that deleted passages be restored before the arduous job of line-by-line revisions can even begin.
"The text... Cannot be used as a basis for negotiation, as it is unbalanced," the African Group said in a statement released hours before the opening session.
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The new draft "does not reflect the African Group positions, and crosses the group's red lines," it said.
The African nations' viewpoint is shared by other blocs under the more than 100-strong "G77 plus China" umbrella.
One make-or-break issue is finance.
Rich nations have pledged to mobilise USD 100 billion per year from 2020 to help vulnerable countries reduce their greenhouse gas emissions and cope with the impacts of global warming.
Developing nations want firm commitments, not just on the total amount but also where it will come from and what it will be used for. They favour public monies, and demand that funds be balanced between mitigation -- cutting carbon emissions -- and adaptation.
There is nothing, for example, "on the obligations of developed countries to provide the means of implementation" for relevant technology, he told AFP.