If Wen and Obama do get the chance to meet, they will likely have lots to talk about - the US recently urged China to accept a binding carbon reduction target and said it will not provide financial support to Beijing for climate initiatives.

China, meanwhile, called on the US to set a more ambitious target for emissions reduction after Washington promised to cut them by around 4 percent by 2020 from the 1990 base. Developing countries had urged the US and wealthy countries to slash emissions by 40 percent.

Experts have called on the US and China to narrow their differences in a bid to ensure the conference is a success.