With just weeks to go before UN talks on climate change open in South Africa, negotiators have shifted their goal from striking a historic deal to ensuring that the global system survives.

Participants have long billed the conference opening on November 28 in Durban as a last chance to find a way forward on fighting climate change, with the Kyoto Protocol's commitments to cut carbon emissions expiring after 2012.

Officials from key nations reported progress in preparatory talks that closed Friday in Panama City -- not in resolving the most knotty issues, but in starting to work out a technical framework for the future.

"Countries are trying pretty hard to scale expectations down to a realistic level for Durban," said Jennifer Haverkamp, the international climate program director at the US-based Environmental Defense Fund.

Haunting the talks is the 2009 summit in Copenhagen, where more than 100 world leaders swept in as public pressure mounted for a sweeping deal but found themselves ready only to take incremental steps.

Politics have also shifted in the United States, the world's largest economy. Proposals to cut carbon emissions nationwide floundered in Congress as President Barack Obama's rivals question the science behind climate change.

US negotiators have pushed vigorously in talks for China, the world's largest emitter, to face binding obligations. But Beijing and other emerging economies have hit back that Washington must make firmer commitments.

"We're probably some years away from the comprehensive, robust agreement that we need as long as the United States comes to these negotiations with empty pockets," Haverkamp said.

Greenpeace climate activist Tove Ryding conceded that governments would not be able produce an ambitious agreement in Durban.

"However, the least they can give us are solid building blocks towards that agreement as well as a timeline and a plan to ensure that we will get that agreement as fast as humanly possible," she said.

UN-led scientists say that carbon emissions must peak by mid-decade to avoid the worst impacts of climate change. As of now, combined national commitments put the planet far away from meeting a goal of checking warming to 2.0 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels.

Mahlet Eyassu, an activist with Forum for Environment-Ethiopia, pointed to this year's drought in her region. The United Nations says that tens of thousands have died from famine, mostly in war-torn Somalia, and millions more are at risk.

"The Horn of Africa has been affected by the worst drought in 60 years. So countries need to be more serious. They need to take urgent actions" on climate change, she said.

Most governments support the preservation of the UN Framework Convention on Climate Change and its rules-based system, even if they disagree strongly over where those rules should apply.

Dessima Williams, a diplomat from Grenada who represents a bloc of small island states that fear rising water levels threaten their very existence, saw some progress in Panama and said it would benefit the international order.

"We must preserve the multilateral rules-based climate regime to limit greenhouse gas emissions to ensure the survival of small island states and the planet," she said.

Many delegates agreed that the Panama talks made headway on finance, with technical details being worked out on a Green Climate Fund that aims to provide $100 billion a year to the most vulnerable countries starting in 2020.

But there was no sign of agreement on emissions cuts after 2012. Only the European Union has offered a new round under the Kyoto Protocol, which only covers wealthy economies and does not require reductions by China.

UN climate chief Christiana Figueres said that one solution would be for some economies to recommit under Kyoto "to uphold the rules-based system," with other nations making pledges that are "rigorous" but outside the treaty.

"Governments are exploring precisely those middle-ground solutions," she said. "That is going to be the crux of Durban."