Half-way through crucial talks to breathe life into the Paris climate deal negotiators haggled over how to share out the cost of curbing global warming and struggled to pare down a sprawling text.
The two weeks of talks, which began at the start of the week, are billed as the most important UN conference since the Paris 2015 agreement on climate change. The goal is to meet an end-of-year deadline for agreeing a rule book on how to enforce action to limit global warming.
By the end of Saturday, negotiators aim to have a simplified draft ready for high-level ministerial debate that starts on Monday.
The challenge is to ensure any rule book agreed in Katowice is accompanied by ambition and to resolve deep-rooted tensions between the developed and developing world over how to finance change.
"We're in the initial period, so everybody is flexing their muscles. It's not the time for concessions yet," one delegate said on condition of anonymity.
Delegates said a big issue was how to provide certainty for developing countries that promises of future finance from the richer world would be forthcoming.
He said there were still around 800 brackets in the text, indicating points of disagreement, but that compares with nearly 3,000 before the talks in Katowice began.
Territorial concerns have also complicated discussion.
"There are many discrepancies about emissions reporting and monitoring, especially when it comes to sharing the data with other countries," one delegate said, speaking on condition of anonymity.