Negotiators representing nearly 200 nations worked through the night and well into the day Saturday, with hopes of leaving Durban with solid deals in place.

Among the key issues being discussed is whether to adopt a second commitment period of at least five years to the Kyoto Protocol - a pact, enacted in 2007 that legally binds governments to cut emissions.

The current proposal being considered would extend the Kyoto Protocol for another term, if, in exchange, the United States, China and other big countries that are not a part of it, agree to negotiate a future replacement deal to cut emissions after 2020.

But even if a deal is reached here in Durban, some observers say the terms are still insufficient to combat climate change. Alden Meyer is from the Union of Concerned Scientists.

 It's all well and good to talk about long-term treaties post 2020, and that's essential and we support that and want to get a decision here launching a process to do that. But we also need a near term process to raise the level of ambition collectively, both developed and developing countries, to try to substantially raise efforts to close what's called the gigaton gap, which is the gap between the emissions reductions we have on the table and those that have to be made to stay under two degrees.

Two degrees centigrade is the amount by which scientists say the Earth can warm before causing irreversible damage to life systems. Another big issue is setting up the Green Climate Fund, which is supposed to provide financing for environmental projects in developing countries.

Countries have had a hard time agreeing on what sources of funding will be used for the fund, and on other technical aspects. Harjeet Singh of ActionAid says it looks increasingly unlikely there will be a complete fund before the next climate conference in Qatar.

Things are not looking very positive on the Green Climate Fund we see that the operationalization that we were expecting to definitely have happened in Durban, it's not really happening.

It has been moved to next year so between now and Qatar it may happen sometime, which is quite depressing. Singh said the United States, which has been asking that private firms have more access to the fund, is largely responsible for the delay.

Time is running out for a major deal to combat climate change, and many environmental ministers involved in the talks have already started heading home.

Some of the employees at the conference center have been asked to be available to work again on Sunday, suggesting negotiations may have a long way to go. Gabe Joselow, VOA news, Durban.