Frustrated negotiators enter the final day Friday of a halting round of crunch UN talks to forge a workable draft for a climate rescue pact to be inked by the year's end.

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 will be 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.

Delegates said 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 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," he said in a statement.

Most developed nations, while agreeing the pace was too slow, believe line-by-line revision at this point would slow things down, and want to hand the job of reworking the text over to the co-chairmen of the UN negotiations.

- Stakes are high -

The Paris agreement is meant to slow the march of dangerous global warming by slashing climate-altering greenhouse gas emissions from mankind's unbridled burning of fossil fuels.

The overarching goal is to limit average warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.

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.

"Everyone thinks it's up to the other guy to move things forward," said Pierre Radanne, a climate analyst who advises African countries on policy.

"Everyone says: 'we're not making progress' but no one says: 'I'll withdraw this or that proposal'. Nobody wants to give up anything essential."

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.