The head of the US delegation at UN climate talks has warned of a “major breakdown” in the process if negotiators fail to come to an agreement at a meeting in Lima, Peru.
Talks remain deadlocked by divisions between rich and poor countries over the scale and scope of plans to tackle global warming.
The talks were due to have concluded on Friday but have now overrun.
Disagreements abound over a key building block of a new global treaty.
That element, known as Intended Nationally Determined Contributions (INDCs) in the jargon of the meeting, is seen as a major step as developed nations are due to make pledges on how they will tackle climate change by the end of March next year.
The countries came to Peru to work out the details of what those pledges would entail.
It has not been smooth sailing.
