King Charles III told world leaders on Friday that the UN's COP28 climate talks in Dubai must be a "critical turning point" in the fight against climate change, with "genuine transformational action".

Charles kicked off two days of speeches by heads of state and government in the sun-soaked Gulf city of Dubai, where the future of fossil fuels has taken center stage.

"I pray with all my heart that COP28 will be another critical turning point towards genuine transformational action," Charles told assembled leaders including Indian Prime Minister Narendra Modi, French President Emmanuel Macron and Brazilian President Luiz Inacio Lula da Silva.

"The Earth does not belong to us, we belong to the Earth," said the king, a lifelong environmentalist, who missed last year's COP27 in Egypt reportedly due to objections by then UK prime minister Liz Truss.

The COP28 conference opened on Thursday with an early victory as nations agreed to launch a "loss and damage" fund for vulnerable countries devastated by natural disasters.

But delegates face two weeks of tough negotiations on an array of issues that have long bedevilled climate talks, starting with the future of oil, gas and coal.

Phase down vs phase out

A first draft of the agreement being negotiated by nearly 200 countries includes language on a "phasedown/out" of fossil fuels, which account for the bulk of greenhouse gas emissions.  

The sense of urgency was heightened by a UN warning that 2023 is on track to become the hottest year on record, raising fears the world will not meet the goal of limiting warming to 1.5 degrees Celsius.

"The science is clear: the 1.5-degree limit is only possible if we ultimately stop burning all fossil fuels," UN Secretary-General Antonio Guterres said.

Activists have raised concerns about the influence of the energy industry lobby at COP28 as the conference is chaired by Sultan Al Jaber, who is also head of the UAE's national oil company.

Jaber, who is also chairman of a renewable energy firm, said Thursday the "role of fossil fuels" must be included in a final COP28 deal.

"I will be rolling up my sleeves, engaging and helping address this challenge and delivering real, actionable results," Jaber said.

The draft text sets up a fight between those calling for a "phaseout" and those in favour of a less drastic "phasedown" of fossil fuels. But observers said the inclusion of such language was significant.

"It is more ambitious than anything ever tabled at COP27 (talks in Egypt last year), so even having it among the options is a big step up," said Lola Vallejo, an expert from French climate think tank IDDRI.

Gaza war

More than 140 kings, presidents and prime ministers will address delegates on Friday and Saturday.

But the climate crisis will share the agenda with the Israel-Hamas conflict.

Israeli President Isaac Herzog met his UAE counterpart Sheikh Mohamed bin Zayed Al Nahyan on Thursday and will be among the speakers addressing the COP28 conference on Friday.

Palestinian president Mahmud Abbas had also been scheduled to speak but his office told AFP that he was no longer going and his foreign minister would be in Dubai instead.

The conference began on Thursday with a moment of silence — at the request of the Egyptian head of last year's COP — for the civilians who have died in the conflict.

The war began on 7 October when Hamas and other militants from Gaza poured over the border into Israel, killing around 1,200 people, mostly civilians, and kidnapping about 240, according to Israeli authorities.

Aiming to destroy Hamas, Israel retaliated with an air and ground offensive that the Hamas government in Gaza says has killed more than 15,000 people, also mostly civilians, and reduced large parts of the north of the territory to rubble.

Herzog is using his COP28 visit for a diplomatic push to secure the release of hostages held by Hamas.

He "appealed" to his Emirati counterpart "to employ his full political weight to promote and speed up the return home of the hostages," the Israeli president's office said.

US Vice President Kamala Harris, who will represent the United States at COP28, will meet with regional officials on the Israel-Hamas conflict, according to the White House.

As part of a week-long pause in fighting, Hamas freed dozens of hostages taken during last month's attack on Israel in exchange for the release of more than 200 Palestinian prisoners being held in Israeli jails.