An Australian campaign to get other nations to accept its definition of carbon dioxide emissions has so far failed, raising doubts over whether Prime Minister Malcolm Turnbull can easily deliver the 5 per cent cut in emissions his government has promised. 
At stake is whether Australia will be deemed by the United Nations to be on course to reach its goal of cutting emissions by 5 per cent by 2020 (compared with 2000) - as the government says will comfortably be achieved - or whether they are actually calculated to be rising.
"Regrettably no agreement on draft decisions on the methodological issues under the Kyoto Protocol could be reached, despite investing a great amount of time in the particular item," a statement from the conference said.
This it would affect "the decision on the organisation of the review of inventories and initial report of Annex I Parties [of developed nations] under the Kyoto Protocol," it said.
It is understood a plenary session on Friday will be the last chance to resolve the impasse that remained after negotiations ran late on Thursday without a breakthrough. Without an agreement over the definition of emissions at Paris, there may not be another chance until   June.
Mr Turnbull drew applause from fellow leaders on Monday when he announced Australia would ratify the second stage of the Kyoto Protocol - a declaration that surprised some delegates since key rules that had implications for Australia were yet to be settled.
A spokesman for Environment Minister Greg Hunt, who is attending the Paris summit, said on Friday that the government's position hadn't changed.
"The Prime Minister's statement was clear and categorical that Australia will be ratifying," he said.
"We will be ratifying.
"Talks on technical matters are ongoing." Without a last-minute resolution, a failure of the negotiations on the pre-2020 rules may have implications for the climate summit.
The conference aims to secure a credible post-2020 pathway for nations to cut greenhouse gas emissions to keep global warming to less than 2 degrees of pre-industrial levels.
Key developing nations agreed on a 2015 deadline for a new global agreement at the Durban gathering in 2011 in part because the European Union and Australia signalled they would make progress on ratifying the second phase of the Kyoto Protocol.
It is understood that not delivering on this part of the Paris negotiations means the EU and Australia have broken their part of the 2011 deal.
As reported earlier, Australia met resistance during the Paris summit to the inclusion of deforestation in the definition of emissions covered to 2020.
Including deforestation allows Australia to meet pollution goals even as emissions from industrial and other sources rise.