The incoming head of the UN climate convention has said rich nations must pledge bigger emission cuts if climate change is to be tackled effectively.
But Christiana Figueres said she was confident that leaders would meet the challenge "because humanity has to meet it - we don't have another option."
Ms Figueres was speaking at a two-week session of UN negotiations in Bonn.
She said the mood was "constructive"; but major differences are evident between different groups of countries.
In particular, some developing countries are angry at what they see as western nations' attempts to insert new loopholes into regulations on how emissions from land use change are accounted for, which could allow western nations to cut actual emissions by less than they have pledged.
Developing countries are also once again asking for more ambitious cuts from the west.