United Nations climate chief Yvo de Boer is warning that progress is too slow at the climate conference in Copenhagen.
The two-week conference will end later this week, with hopes of a deal emerging now resting with world leaders who are beginning to arrive.
Mr de Boer says there has been a lot of good work done over the past week in some areas, but it has not been enough.
He says ministers will have their work cut out for them when the high-level segment of the conference begins.
Conference president Connie Hedegaard also says there is still a lot of work to deliver what people around the world, expect them to deliver.
German Chancellor Angela Merkel has told reporters in Berlin that she is nervous about the lack of progress at the conference.
New Zealand Climate Change Minister Nick Smith says the next 48 hours are crucial to securing a deal.
He told Morning Report that ministers will be working late into the night to try to make the conference a success.
Dr Smith said there's been too little progress on many issues over the past two years, which is why maximum effort has to be put in over the next two days.