Dubai (AFP) – Negotiations over the future of fossil fuels heated up at UN climate talks on Saturday, with OPEC catching flak over the oil cartel's push to block any phase-out in the final deal.

The tone has veered between optimism and concern about the pace of talks as negotiators have held marathon sessions aimed at finding a compromise on the fate of oil, gas and coal.

OPEC added fuel to the fire after it emerged that its Kuwaiti secretary general, Haitham Al Ghais, sent a letter to the group's 13 members and 10 allies this week urging them to "proactively reject" any language that "targets" fossil fuels instead of emissions.

"I think that it is quite, quite a disgusting thing that OPEC countries are pushing against getting the bar where it has to be," Spanish ecology transition minister Teresa Ribera, whose country holds the rotating EU presidency, told reporters.

Dramatically scaling up the deployment of renewable energy while winding down the production and consumption of fossil fuels is crucial to achieve the global goal of limiting warming to 1.5 degrees Celsius.

The High Ambition Coalition, a broad group of nations ranging from Barbados to France, Kenya and Pacific island states, also criticised the OPEC move.

"Nothing puts the prosperity and future of all people on Earth, including all of the citizens of OPEC countries, at greater risk than fossil fuels," said Tina Stege, climate envoy for the Marshall Islands, which chairs the coalition.

"1.5 is not negotiable, and that means an end to fossil fuels," Stege added.

Iraq supports OPEC

A third draft deal released Friday offers various ways to phase out of fossil fuels, but it also includes the option to not mention them at all in the final text.

Saudi Arabia had until now been the most vocal country against a phase-out or phase-down of fossil fuels.

In the OPEC letter sent Wednesday, Ghais said it "seems that the undue and disproportionate pressure against fossil fuels may reach a tipping point with irreversible consequences".

Assem Jihad, spokesman for Iraq's oil ministry, told AFP his country supports the OPEC letter.

Iraqi oil minister Hayan Abdel Ghani "has rejected attempts to target fossil fuels", Jihad said.

He added that Ghani has tasked Iraq's COP28 delegation to "ensure that the wording of the final statement puts the emphasis on world cooperation on a reduction of emissions in order to preserve the environment and climate".

But another OPEC member, COP28 host the United Arab Emirates, has taken a conciliatory tone throughout the negotiations and acknowledged that a phase-down was "inevitable".

'Critical stage'

Canadian climate minister Steven Guilbeault told AFP he was "confident" that the final text would contain language on fossil fuels.

Guilbeault is among a group of ministers who have been tasked by COP28 president Sultan Al Jaber to shepherd the negotiations and find an agreement by Tuesday, when the summit is due to end.

"It's a conversation that will last a few more days," Guilbeault said.

"Different groups are talking and trying to understand on what we could agree, but it's still quite an embryonic conversation," he added.

German climate envoy Jennifer Morgan said countries were "now moving into the critical stage of negotiations" but she was "concerned that not all are constructively engaging".

Fresh calls for a phase-out were made by ministers addressing a plenary session on Saturday.

"We are extremely concerned about the pace of the negotiations, given the limited time we have left here in Dubai," said Toeolesulusulu Cedric Schuster, chairman of the Alliance of Small Island States (AOSIS).

AOSIS has pushed hard for a phase-out, warning that their nations were on the frontlines of climate change, with rising seas threatening their existence.

"I implore you, let this COP28 be the summit where we leaders are remembered for turning the tide," Schuster said, adding that stepping up renewable energy "cannot be a substitute for a stronger commitment to fossil fuel phase-out."