Negotiators are battling 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.
After last week's haggling, the co-chairs of the meeting released two synthesis documents on Monday reflecting the 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 on Tuesday.
But several nations are not happy.
The text on national pledges, dubbed Intended Nationally Determined Contributions or INDCs, remain "the subject of a lot of disagreement," said US envoy Todd Stern.
The UN has set a target of curbing average global warming to 2C 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.
But developed nations point the finger at major developing emitters such as China and India that rely heavily on fossil fuel to power their rapid growth.
Washington and Australia, among others, insist 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.
Earlier on Monday, Australia's Foreign Minister Julie Bishop said: "Those countries that are emitting the most have the greatest responsibility in terms of the totality."
"The world doesn't stop. The world keeps changing and it has been changing in a material way," said Stern.
"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."
The EU, for its part, said 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 term for emissions cuts.
South Africa, a member of the developing nation negotiating bloc, 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, with China emerging as a strong opponent last week.
But Canete said: "We must have an evaluation (or) we will not know whether we are ambitious enough."