Negotiators battled it out over draft text for a UN pact to curb global warming, on the eve of ministers and the UN chief arriving in Lima to shift the talks into higher gear.
With under five days of negotiating time left, parties remain deeply divided on key aspects of a deal they undertook to ink in Paris in December next year, and to implement from 2020.
The Lima talks have two main tasks: drafting a negotiating outline for the Paris deal and reaching agreement on the 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 there be differentiation in the responsibility assigned to rich and poor nations for curbing Earth-warming greenhouse gas emissions?
Must rich nations commit in writing to financing, and to climate adaptation aid to the developing world?
Will pledges be assessed for adequacy?
After last week's haggling, the co-chairs of the meeting released two synthesis documents Monday reflecting the wide variety of views.
These draft decision texts will form the basis for political negotiations, with dozens of ministers and UN chief Ban Ki-moon joining the dialogue Tuesday.
But several nations are not happy.
The text on national pledges, dubbed Intended Nationally Determined Contributions or INDCs, remains "the subject of a lot of disagreement," said United States envoy Todd Stern.
- Soaring greenhouse emissions -
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 greenhouse gas emissions -- requiring a costly shift from cheap and abundant fossil fuels to less polluting energy sources.
Developing countries want rich nations to bear bigger responsibility for the curbs, given their much longer history of pollution and superior technology and resources.
But developed nations point the finger at major developing emitters like China and India that rely heavily on fossil fuel to power their rapid growth.
Washington, among others, insists responsibility can no longer be classified in terms of the 1992 UN Framework Convention on Climate Change, which divided the world into Annex 1 rich, and Annex 2 poor nations, and set emissions goals only for the first group.
"To say that you're going to frame the structure, the form and content of the agreement based on who was in which category in 1992 seems to us to be untenable as a manner of dealing with the substantive problem of climate change, and also untenable politically for developed countries," said Stern.
Earlier 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."
But Khalid Abuleif, negotiator for oil-producing giant Saudi Arabia, cautioned "there should not be winners and losers."
"If we let climate change happen then we do have losers, like the small islands, the least developed countries... and if we take inappropriate actions to address climate change we will create another group of losers, therefore vulnerabilities have to be taken into account," he said.
- Adaptation 'red line' -
The EU, for its part, said Monday adaptation and finance guarantees should not form part of the INDC text, as demanded by developing nations.
"We have to address adaptation, but not in the INDCs... The INDCs should be limited to mitigation," said EU climate commissioner Miguel Arias Canete.
Mitigation is the climate jargon for emissions cuts.
South Africa, a member of the developing nation negotiating bloc, however, insists that adaptation wording in the pact is a "red line."
Another sticking point is whether there must be an assessment of national pledges and their global impact on the two-degree goal.
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.
Ministers will meet Tuesday on the tough issue of climate finance, followed Wednesday by talks on the hot potato of "differentiation."
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.