A UN climate summit in Dubai made progress Saturday but deep divides persisted, negotiators said, following a last-minute push by the OPEC oil cartel to block a phase-out of fossil fuels.

OPEC drew outrage from green-minded countries and activists when it joined Saudi Arabia and called on members to block an emerging declaration that would seek to wind down extraction of the oil, coal and gas which are fuelling the climate emergency.

But both the president of the COP28 summit, Sultan Al Jaber, and top oil importer China said they saw headway as talks go into a marathon phase before the scheduled close on Tuesday.

"The window is closing to close the gaps. We are making progress, but not fast enough and not satisfying enough," Jaber said.

Jaber has drawn skepticism from environmentalists as he leads the UAE national oil company, but he has taken a more moderate stance than Saudi Arabia by saying cuts in fossil fuels are "inevitable".

"Now is the time to put aside self-interest for the common interest," Jaber told delegates in a Saturday night session, without publicly endorsing any option.

Jaber said he hopes to submit a package for review by Monday morning.

A third draft of a deal, released on Friday, offers various ways to phase out fossil fuels but also includes the option to avoid the issue entirely.

Summit success tied to issue

China said it was working to find a solution that was "acceptable to all parties".

"I think we've already had some progress on this issue and I believe we will have more progress in resolving this very soon in the coming few days," China's climate negotiator Xie Zhenhua told reporters.

"Because if we do not, if we do not resolve this issue, I don't see much chance in having a successful COP28," he said.

Canadian climate minister Steven Guilbeault told AFP he was "confident" the final text would contain language on fossil fuels, which emit planet-heating greenhouse gases.

OPEC Secretary-General Haitham Al Ghais in a letter made public Friday urged the cartel's 13 members and 10 allies to "proactively reject" any language that "targets" fossil fuels rather than emissions.

In a speech read in his name to the summit, Al Ghais said there was "no single solution" for sustainable energy.

"We need realistic approaches to tackle emissions, ones that enable economic growth, help eradicate poverty and increase resilience at the same time," the speech said.

Teresa Ribera, the ecology transition minister of current European Union president Spain, said it was "quite a disgusting thing" for OPEC countries to be "pushing against getting the bar where it has to be".

French Energy Minister Agnes Pannier-Runacher said the OPEC statement left her "stunned" and "angry".

Planetary crisis

The planet has endured a string of record-breaking temperatures and intensifying storms and heatwaves, with efforts far off track on an ambition set at the 2015 Paris summit to limit warming to 1.5 degrees Celsius above pre-industrial levels.

"1.5 is not negotiable, and that means an end to fossil fuels," said Tina Stege, climate envoy for the Marshall Islands, which like many low-lying ocean nations fears its very survival as melting ice brings up water levels.

A negotiator from a country in favour of a fossil fuel exit said the Arab group of nations was the only one to take a strong position against a phase-out, although cracks were seen with Arab states that do not produce oil.

A person working for the summit president's office played down objections by Saudi Arabia, saying it was normal for nations to push hard at the end.

"I don't feel that we're at that point where one is sticking their head above the parapet and being the troublemaker," the person said on condition of anonymity.

Colombia, whose left-leaning government has aggressively promoted environmentalism, warned that COP28 was also failing on raising financing for countries to adapt to the effects of climate change.

If countries block "goals on adaptation but at the same time oppose the phase out fossil fuel, they need to be held accountable. And that accountability should be seen financially", Colombian Environment Minister Susana Muhamad said.

Next year's climate talks are likely to be held in another major producer of fossil fuels as Azerbaijan announced it had secured a consensus to host COP29.