Battle lines on fossil fuels hardened at UN climate talks yesterday despite scientists warning that global warming could breach the 1.5C threshold within seven years.

A new COP28 draft agreement in Dubai included the options of phasing out fossil fuels or not addressing the issue at all, setting the stage for tough negotiations due to end next week.

Saudi Arabia -- the world's biggest oil exporter -- took a hardline stance, saying it would "absolutely not" agree to phasing down fossil fuels, never mind phasing them out.

The thorny debate over the future of fossil fuels, the biggest cause of global warming, is the key battleground at the COP28 meeting hosted by the oil-rich United Arab Emirates.

The latest version of a potential agreement included three options -- an "orderly and just" phase-out, faster efforts to phase out fossil fuel projects that do not capture and store emissions, or "no text" on the subject.

An earlier draft, prepared by the UK and Singapore, that proposed a "phasedown/out" was badly received by delegates, a Latin American negotiator told AFP.

"Everyone was extremely unhappy with the first draft," the negotiator said, requesting anonymity.

"When we started talking... everything collapsed... There is pretty much nothing on the way forward," the delegate added.

Saudi Arabia's energy minister said he would "absolutely not" agree to a phase-down of fossil fuels in the COP28 agreement.

"I would like to put that challenge for all of those who... come out publicly saying we have to (phase down)," Prince Abdulaziz bin Salman told Bloomberg. "Call them and ask them how they are gonna do that?"

Laurence Tubiana, the architect of the landmark Paris climate accord in 2015, said the negotiations are "difficult because we're at a stage where all options are on the table and we don't see a balancing point".

"On one hand it's normal at this stage but it seems particularly difficult because we're talking about the elephant in the room, which is fossil fuels," Tubiana told AFP.

Nearly 2,500 fossil fuel lobbyists -- a record -- have been accredited for UN climate talks in Dubai, campaign groups said.

The NGO umbrella group Kick Big Polluters Out said 2,456 people tied to fossil fuel interests were identified, roughly four times the number at COP27 last year.

If taken as a group they outnumber "every country delegation" apart from Brazil and the UAE, the coalition added.

Campaigners have worried about the influence of the fossil fuel lobby since Sultan Al Jaber, the head of the UAE's national oil company ADNOC, was named president of COP28.

The annual Global Carbon Project estimated yesterday there is a 50 percent chance warming will exceed the 2015 Paris deal's goal of 1.5 degrees Celsius over multiple years by around 2030.