UN Secretary General Ban Ki-Moon says climate change negotiations have been moving slowly.

But, adds that, as major international players gather in Copenhagen, he remains optimistic that a deal still can be reached.

Ban Ki-Moon, UN Secretary General, said, "Unfortunately, negotiations have been going very slowly and, even at this time, negotiations are still going. This is one of the most complex, and complicated, and most difficult process, as you may imagine. But I have not seen anything that indicates we cannot seal a deal in Copenhagen. I believe we can seal a deal, still, in Copenhagen."