The UN secretary-general flew back to the climate talks in Poland to deliver an emergency address on Wednesday, urging countries to reach agreement on a widening set of issues that threaten to stall the process. “To waste this opportunity would compromise our last best chance to stop runaway climate change,” António Guterres told the audience of ministers and negotiators from nearly 200 countries. “It would not only be immoral, it would be suicidal.”

The aim of the talks is to agree a set of rules for how to implement the Paris climate agreement, which was signed in 2015 and aims to limit global warming to well below 2 degrees Celsius. The negotiators have less than three days to reach consensus before the talks officially end on Friday, although the talks may extend into the weekend due to the current deadlock.

As high-level ministers arrived this week to take over the most difficult political issues, the faultlines between rich and poor countries, and between fossil fuel-based economies and non-fossil fuel economies, have become more clear. Saudi Arabia, which has long been seen as a gadfly at global climate negotiations, added to the tensions with a strongly worded statement on Wednesday night, warning about what it called a “sharp deviation from the provisions agreed in Paris”.

The statement from energy minister Khalid al-Falih called for more investment in fossil fuels, and said that the UN talks had been too focused on energy and on oil in particular. Financing commitments are also emerging as a potential flashpoint, with less developed countries asking for commitments from rich countries to fund their climate efforts.