Frustrated negotiators hoped for a last-minute breakthrough Friday as they wrap up a fraught round of UN talks in Germany to forge a climate rescue pact to be adopted by the world's nations in December.

Diplomats have lamented the "snail's pace" of this week's haggle in Bonn, accusing one another of rehashing well-rehearsed positions and holding up the real work of line-by-line text bartering.

Friday was the sixth-to-last negotiating day, with five more to follow in October, before the highly-anticipated November 30-December 11 UN conference opens in Paris in the presence of heads of state.

Negotiators are aiming to produce an agreement to slow the march of dangerous global warming by slashing climate-altering greenhouse gas emissions from mankind's unbridled burning of fossil fuels.

"We have seen an increasing number of areas of convergence during the week, but it is evident that a radical step-change in now necessary," European negotiator Elina Bardram told AFP.

Diplomats have lamented the "snail's pace" of a round of crunch UN talks in Bonn to forge a workable draft for a climate rescue pact to be inked by the year's end Mujahid Safodien, AFP/File

"We see very senior, experienced negotiators very frustrated because they are itching to get to the line-by-line negotiations, which we very much need to take place before we get to Paris."

It seemed inevitable that delegates will ask the joint chairmen of the UN forum to continue text-crafting after the meeting closes on Friday.

The goal is to present negotiators with a more workable draft version when they next meet in Bonn in October.

"For the sake of expediency, the co-chairs will need to prepare a basis for negotiations well ahead of the next session in October," said Amjad Abdulla, a negotiator for the Alliance of Small Island States.

"We hope it reflects the areas of common understanding found this week so we can hit the ground running in Bonn and build momentum for a successful outcome in Paris."

The co-chairmen of the forum said they were "prepared" to take on this task.

Climate negotiators need a more workable draft version when they next meet in Bonn in October Mehdi Fedouach, AFP

It would be "based on positions expressed here" in Bonn, said Ahmed Djoghlaf, adding "this document will be ready in October."

His colleague Daniel Reifsnyder added: "What I hope we will be able to do next time is something that will truly be a better base for parties.. to negotiate."

Delegates say the Bonn preparatory round, which opened Monday, made piecemeal progress on some of the detailed discussions, but the overall objective of a universal deal remained far off.

Developing countries, in particular, were disappointed that the working document produced in Geneva in February -- a laundry list of often contradictory options for solving the pressing problem of global warming -- was still essentially the same.

"The time for talking about concepts and general chit chat is over," said on Thursday Gurdial Singh Nijar, a Malaysian negotiator and spokesman for the Like Minded Developing Nations bloc, which includes China, India, and many African, South American, Middle Eastern and Asian countries.

"Only through direct, inclusive and interactive negotiations will parties be able to narrow down differences, find convergence and ultimately achieve consensus."

Djoghlaf agreed: "yes, we are not there," but added: "We are in the politics of small steps... in the right direction."

- Stakes are high -

The overarching goal of the agreement to be sealed in the French capital is to limit average warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.

Global powers are seeking a deal to limit warming to two degrees Celsius (3.6 degrees Fahrenheit) Dominique Faget, AFP

Fundamental divisions remain over how to share out carbon-emissions cuts between rich nations, which have polluted for longer, and emerging giants such as China and India powering fast-growing economies and populations.

The last attempt at forging a universal climate deal, at a UN conference in Copenhagen in 2009, came undone, and nations are loath to repeat history.

A timely reminder of the urgency came on Wednesday, when scientists warned that on current carbon-cutting pledges, the world was on track for warming of three degrees Celsius, a sure recipe for catastrophic storms, droughts, disease spread, water shortages and sea level rise.

"Our fear is this will end up in a lowest-common-denominator situation, which is nobody would agree with anybody and then everybody just agree on the least ambitions option" for an agreement, Greenpeace climate campaigner Li Shuo told AFP.

"The question is not whether or not we will have a deal. But i think the quality of the deal is in question."