The Emirati head of the UN's climate conference pressed countries on Wednesday to strive for common ground and reach a "historic" deal by early next week, giving negotiators days to untangle disagreements over the fate of fossil fuels.

It is rare for UN climate talks to end as scheduled but COP28 president Sultan Al Jaber set the ambitious goal of having a deal in place by 11:00 am (0700 GMT) on Tuesday, the last official day of the conference.

He urged the nearly 200 nations represented at COP28 to work with a "spirit of compromise", step out of their "comfort zones and find common ground to deliver a high ambition and balanced outcome".

COP28 kicked off last week with the landmark launch of a loss and damage fund for nations devastated by climate change.

But the first week of negotiations ended on Wednesday with delegations unable to produce an updated version of a draft agreement that was published the previous day.

The text includes language on phasing out fossil fuels, which the European Union, the United States, island nations and African countries support.

But it also has an option to leave the issue off the final text, a position backed by China, Saudi Arabia and other Arab nations.

Scientists warn that greenhouse gas emissions -- the bulk of which come from burning fossil fuels -- must fall by 43 percent by 2030 from 2019 levels for the world to reach the ambitious goal of limiting warming to 1.5 degrees Celsius.

"I will continue to ask parties to bring bridging proposals on fossil fuels, renewables and energy efficiency, in line with the science," Jaber said at the end of a plenary session capping the first week.

Climate campaigners have viewed Jaber with deep suspicion due to his position as the head of UAE national oil firm ADNOC, but he has sought to ease concerns by stating that a phase down of fossil fuels was "inevitable".

- 'Heavy on posturing' -

The COP28 conference takes an official day off on Thursday before resuming on Friday, with ministers taking over the final days of negotiations.

UN climate chief Simon Stiell complained that the draft text was a "grab bag of... wish lists and heavy on posturing".

"At the end of next week, we need COP to deliver a bullet train to speed up climate action. We currently have an old caboose chugging over rickety tracks," he added.

The Alliance of Small Island States, which includes some of the world's most climate-vulnerable countries, called for "major emitters to enhance their commitments".

"If we fail, the consequences will be catastrophic," the alliance's chairman Cedric Schuster said.

The latest text includes a new phrase calling for an "orderly and just" phase-out.

One person familiar with the talks said the word "orderly" came from Jaber.

The language could signal a consensus candidate as it would give countries different timelines to cut emissions depending on their level of development and reliance on fossil fuels.

During closed-door talks on Tuesday, Saudi Arabia again opposed any mention of fossils, saying it would avoid "the trauma of explaining our position... that is well noted and clear", according to meeting participants.

- 'Temperature will keep rising' -

With flagrant divisions coming to the fore, Europe has called for a harder line.

"I want this COP to mark the beginning of the end for fossil fuels," European climate commissioner Wopke Hoekstra said on Wednesday.

Germany's climate envoy Jennifer Morgan told AFP that "it is necessary that every party move away from their red lines (and) into solutions".

"We need to roll up our sleeves and get it done."

US climate envoy John Kerry said there were still "complicated issues" to resolve but it was "time for adults to behave like adults and get the job done".

A new report by the EU's Copernicus Climate Change Service provided a stark reminder of what is at stake as it reported that 2023 will be the hottest on record.

November became the sixth record-breaking month in a row.

It smashed the previous November heat record, pushing 2023's global average temperature to 1.46C warmer than the pre-industrial era, the service said.

Copernicus head Carlo Buontempo said that "as long as greenhouse gas concentrations keep rising we can't expect different outcomes".