Negotiators pored over draft outlines for a UN pact to curb global warming on Monday, hoping for a breakthrough ahead of the arrival in Lima of ministers and the UN chief.
With a week of talks gone and only five days left, parties remain deeply divided on key aspects of a deal they are supposed to sign in Paris in December next year and to implement by 2020.
The Lima talks have two main tasks: drafting a negotiating outline for the Paris deal and agreeing on a format for carbon-curbing pledges that nations are to submit from the first quarter of next year.
But negotiators do not see eye to eye on some basic questions.
Will the pledges be legally binding on rich and poor nations alike?
Must rich nations commit in writing to financial support for climate adaptation in the developing world?
Will pledges be assessed for adequacy?
After last week's haggling, the co-chairs of the meeting released two synthesis documents on Monday that are meant to reflect parties' views on all of the issues.
These draft decision texts will form the basis for political negotiations, with over 100 ministers and UN chief Ban Ki-moon joining officials in Lima on Tuesday.
The UN has set a target of curbing average global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.
The goal must be met by deep cuts in soaring emissions of greenhouse gases—requiring a costly shift from cheap and abundant fossil fuels to less polluting energy sources.
"Essentially, if we continue as we are, we may drastically rewrite the relationship between humans and the planet, potentially, leading to the mass migration of perhaps hundreds of millions or billions of people," climate economist Nicholas Stern warned Sunday.
"History tells us this could result in long and sustained conflict. These are the stakes we are playing for."
Ban, who hosted a leaders' summit in New York in September that yielded vows of renewed political commitment, will on Tuesday open the "high-level segment" of the talks and meet ministers separately.
Rich nations, including the United States, want the deal to focus on emissions curbs but poor, developing and small island states at high risk of sea-level rises, demand guarantees of global support for adaptation to climate risk and compensation for damage.
Impacts already being felt
"From a developing country perspective... our red line is that the post-2020 agreement has to deal with adaptation," South African negotiator Judy Beaumont told AFP.
"The impacts of climate change are already being felt, particularly in developing countries, and so therefore we already have to be building our capacity for adaptation."
Last week, a UN report said developing nations may need as much as $500 billion per year by 2050 for adaptation.
Developing countries also want rich nations to bear bigger responsibility for emissions curbs, given their much longer history of pollution.
But developed nations point the finger at major developing emitters like China and India that are heavily reliant on fossil fuel to power their rapid growth.
On Monday, coal-reliant Australia's Foreign Minister Julie Bishop said: "Those countries that are emitting the most have the greatest responsibility in terms of the totality".
Another sticking point is whether there must be an assessment of national pledges and their global impact on the two-degree Celsius goal, with China emerging as a strong opponent last week.
Ministers are scheduled to meet Tuesday on the other major point of conflict: climate finance for developing nations.
Scientists say the world is on target for four degrees Celsius, or more, with a resulting increase in extreme events like hurricanes and storms, sea-level rise, floods, droughts and desertification.
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