UN climate meeting enters final day

World leaders and environment ministers have held marathon meetings to settle differences, as United Nations climate talks enter the last 24-hours.

Two-track talks are once again moving forward in Copenhagen. UNFCCC executive secretary Yvo de Boer said negotiation between the two working groups will form the basis for a deal. One focuses on a new climate agreement, and the other on adapting the existing Kyoto protocol.

As major international leaders begin arriving in Copenhagen, UN Secretary General Ban Ki-Moon says he remains optimistic that a deal 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."

US Secretary of State Hillary Clinton said she would do everything possible to come to an agreement, after meeting with British Prime Minister Gordon Brown.

U.N. climate chief Yvo de Boer gestures during a press briefing at the Climate Summit in Copenhagen, Denmark, Thursday, Dec. 17, 2009. (AP Photo/Polfoto/Tariq Mikkel Khan)