A bitter row over fossil fuels has broken out at the COP30 UN climate talks in Belém, Brazil, as the meeting formally runs over time.

At the heart of the row is a disagreement over how strong a deal should be on working to reduce the world's use of fossil fuels, whose emissions are by far the largest contributor to climate change.

The dispute pits groups of countries against each other, but all 194 parties must agree in order to pass a deal at the two-week summit.

Representatives and observers from inside a guarded negotiating room say the talks have become very difficult. One negotiator inside the room told the BBC that there is a lot of fighting.

The talks were meant to finish at 1800 local time (2100 GMT) and will now spill into overtime. However, the cruise ships that many delegations are staying on due to lack of accommodation in Belém depart the city on Saturday, piling on the pressure.

Brazil's President Luiz Inácio Lula da Silva and some countries including the UK want the summit to commit nations to stronger, faster action to reduce their use of fossil fuels. It would advance a deal made two years ago, at COP28 in Dubai, which committed countries to transition away from fossil fuels.

A first draft of an agreement in Brazil offered three options including timeframes, but the latest version has no mention of fossil fuels.

French Environment Minister Monique Barbut stated the deal was being blocked by oil-producing countries - Russia, India, Saudi Arabia, but joined by many emerging countries, adding that as it stands now, we have nothing left.

Speaking to journalists outside the negotiating room, Secretary of State for Energy Security and Net Zero Ed Miliband expressed the UK's determination to advocate for further action on fossil fuels, describing the negotiations as hard, sweaty, and frustrating.

Mr. Miliband emphasized the importance of continuing to pursue an innovative roadmap for fossil fuel transition with the backing of over 80 countries.

Some developing countries are hesitant to support the fossil fuel deal, insisting that richer nations first deliver on their climate finance promises to help them cope with climate change impacts. Aisha Moriana, head of Pakistan's delegation, stressed the immediate need for adaptation financing and the complexities involved in securing such support.

Meanwhile, outside the venue, demonstrators chant fossil fuels out and display banners such as Stop Amazon oil and 1.5C under threat: time to act.

The meeting has been further complicated by issues surrounding deforestation and climate financing, drawing attention to the ongoing struggle for more significant actions against climate change globally.