Oil giant Saudi Arabia is blocking the adoption of a major UN report on oceans and climate change by challenging an earlier UN assessment highlighting the need to slash carbon emissions caused by burning fossil fuels, multiple sources told AFP.

Already deep into overtime, a meeting of the 195-nation Intergovernmental Panel on Climate Change (IPCC) in Monaco remained deadlocked early Tuesday, with delegates tweeting pictures of the rising Sun.

A 30-page executive summary is scheduled for release on Wednesday morning.

"It has been 24 hours and there has been absolutely no compromise from the Saudis," said a participant.

"They are undermining the science underlying this report, and it is despicable."

At issue is what might have been a routine reference to an October 2018 IPCC report on the feasibility of capping global warming at 1.5 degrees Celsius.

That assessment detailed the stark consequences for humanity of piercing that threshold, and the need for deep cuts in the use of fossil fuels.

Saudi Arabia is the world's largest oil exporter, and has raised similar objections to other IPCC reports.

"It really seems like Saudi Arabia only came to this meeting to block any language on 1.5C," a participant in the Monaco meeting told AFP.

Two other sources taking part in the five-day talks confirmed the stand-off, noting that Norway, Britain, France, Canada, Chile the European Union were resisting Saudi proposals to drop any reference to the 1.5 C report, or include a reference to its alleged "shortcomings."

Global warming and pollution caused by humanity's carbon-heavy footprint are ravaging Earth's oceans and icy regions in ways that could unleash misery on a global scale, the IPCC report is set to conclude.

Observed and projected impacts include vanishing glaciers, and expanding marine heatwaves, irreversible sea level rise that could eventually displace hundreds of millions of people, according to a draft seen by AFP.

Under the IPCC's consensus rules, all countries must sign off on the language of a 30-page Summary for Policymakers, designed to provide leaders with objective, science-based information.

The Saudis have rejected a sentence that would read: "This assessment reinforces findings in IPCC Special Report on 1.5 C," along with two other UN science reports released over the six months, one on biodiversity and another on land use and food systems.

The 2015 Paris Agreement calls for capping global warming at "well below" 2C, and 1.5 C if possible.

(Source: AFP)