While stressing the need for a binding agreement on Climate Change at the Copenhagen Conference, UN Chief Ban Ki-moon acknowledged that a binding legal document may not be possible in the upcoming meeting.
"We must have a comprehensive, binding agreement in Copenhagen in December," Ban said, adding, "I am reasonably optimistic that Copenhagen will be a very important milestone. At the same time, realistically speaking, we may not be able to have all the words on detailed matters".
During his meeting with UK Prime Minister Brown, the UN Chief called on developed countries to take the lead in tackling the climate problem.
"First and foremost, the developed countries should lead this campaign, considering all their historical responsibilities, and also considering that they are the countries who have most of the capacities, financial and technological," Ban said.
"We have been engaged in talking to many world leaders, and I appreciate Prime Minister Gordon Brown's initiative for his climate-change funding," he added.
The UN Secretary General has called on industrialised countries to show "political will" to make Copenhagen a success, and agree on ambitious targets for greenhouse-gas emissions by 2020.
"If there is political will, I am sure that there is a way we can conclude a binding agreement in Copenhagen," Ban said.