The head of the United Nations calls on delegates in Copenhagen to 'seal the deal'

Observers at the UN Climate Change conference in Copenhagen say there is a potential showdown looming between the world's two biggest polluters, China and the US. Beijing has once again accused Washington and other rich countries of backing down on their commitments to lower carbon emissions. U.N. Secretary-General Ban Ki-moon tried to ease the tension by saying that rich and poor countries must "stop pointing fingers" and work towards a climate pact.