New Zealand Climate Change Issues Minister Nick Smith says he still believes a deal in Cancun is possible.
Dr Smith says last year's UN climate conference in Copenhagen was a train wreck and Cancun has been about getting the train back on the rails.
He says the style of the rhetoric at this year's conference has been much more constructive, so he remains cautiously optimistic.
Dr Smith says he expects negotiations will go late into the night to try to reach agreement.
However, the BBC reports prospects for a deal appeared to be receding as the event entered its final day.
The ABC reports the fault lines between rich and poor countries are proving too deep to overcome.