Artur Runge-Metzger, the EU's chief climate negotiator, told EurActiv from Cancún that he had not given up hope of signing a deal. "I'm still optimistic," he said. "There is still sufficient time to hammer out the key issues in the conference."
But another source in the European negotiating camp said that while the options being considered had been narrowed down, the "level of ambition must be raised" if the conference was to have a successful outcome.
Dutch Green MEP Bas Eickhout told EurActiv he feared that what he believed were tentative agreements on issues such as REDD (Reducing Emissions from Deforestation and Forest Degradation), technology transfers to poor countries and funding could be lost if a deal was not agreed. "I think the problem is that the sense of urgency at the ministerial level is just not high enough," he said.
Earlier, several environment ministers said failure at the talks in Mexico could undermine faith in the ability of the United Nations to tackle global problems in the 21st century as power shifts toward emerging nations led by China and India.
"I think that what is at stake here is also multilateralism," said European Climate Commissioner Connie Hedegaard. "It's absolutely crucial that this process, which is the only one we have [...] can prove that it can deliver results."
No-one wants car crash of a summit
The talks in Cancún have more humble ambitions than those at Copenhagen last year but there are still yawning gaps over issues such as the future of the Kyoto Protocol for curbing greenhouse gas emissions by rich nations until 2012.
Japan, Canada and Russia say they will not extend the pact unless poorer nations also commit to emissions cuts. Developing nations, especially Bolivia, insist the rich world must lead by setting deeper cuts beyond 2013 before they take on curbs.
"I believe that an ambitious, broad and balanced package is within reach," Mexican Foreign Minister Patricia Espinosa told delegates. "That does not mean that we already have it in our grasp."
China also saw signs of hope on Kyoto. Asked if there was room for a deal, Assistant Foreign Minister Liu Zhenmin said: "I think that will be possible. That is still under discussion."
Shinsuke Sugiyama, a senior Japanese official, said that Tokyo's position was unchanged. But he added: "I don't think anybody would try to make use of any part of the questions at hand to block everything, including us."
"A car crash of a summit is in no-one's interest," UK Climate Change Secretary Chris Huhne added.
One senior delegate said there was progress on several core issues but that other hurdles could arise. Small island states, for instance, want the talks to set an end-2011 deadline for agreeing on a treaty, an idea opposed by Beijing and Washington.
Apart from auctioning emissions permits and transactions levies, the UN task force's report recommended increasing taxes on shipping and aviation, banking and public monies to raise funds. Such measures are not universally popular in the developed world.
Some countries linked deadlock in Cancún to Obama's failure to pass US legislation to curb climate change. All other industrialised nations have already capped their emissions under the Kyoto Protocol.
"We cannot afford to be held hostage by the political backwardness of one developed country," said Tuvalu's deputy prime minister, Enele Sosene Sopoaga. "This is life and death, a survival issue for Tuvalu," he said of rising sea levels.
Burden-sharing not resolved
The success or failure of the summit will be judged in large part by how it resolves the future of the Kyoto Protocol. At heart this is a dispute about who should be held responsible for past emissions and how rich and poor nations should share the burden of curbing future ones.
The 1997 protocol requires emissions cuts by almost 40 industrialised countries from 2008-2012. Developing countries want rich nations to set deeper cuts under Kyoto until 2020, while emerging nations sign up for a separate accord.
At least three developed countries, Japan, Canada and Russia, instead want a single new binding agreement that lists pledges by all nations.
Keep or ditch Kyoto?
A success will be declared if the talks leave open the question of whether the Kyoto Protocol should be the basis for future greenhouse gas emissions cuts.
That would unblock a very modest deal to set up a "global climate fund" to help poor nations, create a mechanism to share clean technologies, protect tropical forests and help the poor adapt to impacts ranging from storms to rising sea levels. Such a deal would fall far short of the goals set at the 2009 Copenhagen summit.
The measures are less important than proving that the unwieldy talks can come up with any agreement at all, as China and India becoming more assertive and rich nations struggle with weak growth.
Failure not an option
Failure in Cancún could squelch any hope of solving climate change any time soon via the United Nations, which demands unanimity from all.
Climate change could become a lower priority for governments, even though the UN panel of climate scientists said world emissions need to peak by 2015 to avoid the worst of more droughts, floods, mudslides and rising seas.
The annual talks would continue but governments might invest less effort, abandoning hopes that the UN is the right place to oversee a shift toward cleaner energy.
That in turn could drive alternative approaches to tackle the problem, perhaps through the G20 or other major economy groups, parallel to, or instead of, the United Nations.
(EurActiv with Reuters.)