( CNN ) -- U.N. Secretary-General Ban Ki-moon on Tuesday urged both industrialized and developing countries to do more during this week 's Copenhagen summit toward reaching an agreement on limiting carbon emissions . With world leaders gathering in hopes of forging a deal to reduce the emissions blamed for increasing global temperatures , Ban told reporters that `` Nature does not negotiate with us . '' `` We have a chance -- a real chance , here and now -- to change the course of our history , '' he said . But both industrialized and developing countries `` can and they must do more . '' `` This is a time to stop pointing fingers , '' Ban added . `` This is a time to start looking in the mirror and offering what they can do more of . '' The divide between rich and poor countries is one of the key fissures at the U.N. climate change conference that is nearing a climax in Denmark . Developing countries object to restrictions which they fear would keep them from following the same path to prosperity that the United States and other industrialized nations took , while developed countries are wary of taking steps that would hinder their own economies . Representatives of more than 100 developing nations walked out on the climate summit Monday to protesting what they called inadequate offers of aid from richer countries . Island states in particular , which are more vulnerable to rising sea levels , are pushing for limits that would reduce carbon emissions enough to limit the expected rise in average global temperatures to 1.5 degrees Celsius ( 2.7 degrees Fahrenheit ) . John Holmes , the U.N. undersecretary-general for humanitarian affairs , said the impacts of climate change are more likely to be felt by developing countries . `` This is something that 's happening now , '' he said . `` Climate change has a human face , and that face is represented in part by the most vulnerable and poorest people in the world . '' The so-called `` High Level Segment '' of the conference , in which world leaders sit down in an attempt to hash out a final agreement , begins on Wednesday evening . Yvo de Boer , executive secretary of the U.N . Framework Convention on Climate Change , told reporters Tuesday that `` nowhere near enough progress '' had been made towards a deal . But Danish Prime Minister Lars Lokke Rasmussen , the summit 's host , said he remained confident an accord could be struck by week 's end if governments were `` ambitious . '' `` We can do this by Friday , '' he said . `` I 've chosen to be optimistic about that . '' Are you in Copenhagen ? Share your images . U.S. Secretary of State Hillary Clinton said Tuesday that Washington is ready to do its part to reduce greenhouse-gas emissions , but other countries must play their part as well . `` Nearly all of the growth in emissions in the next 20 years will come from the developing world , '' Clinton wrote in an opinion piece for the International Herald Tribune . `` Without their participation and commitment , a solution is impossible . ''
U.N. chief Ban Ki-moon : `` We have a chance , a real chance , here and now '' Clinton urges poor nations to help as Copenhagen climate summit heads into home stretch . Score: 6