Ministers from across the planet scrambled on Tuesday to overcome dealbreakers to a historic global pact to fight climate change, showing a rare glimmer of optimism as the deadline approaches.

The 195-nation UN talks have been billed as the last chance to avert the worst consequences of global warming: deadly drought, floods and storms, and rising seas that will engulf islands and densely populated coastlines.

To seal an elusive deal by Friday's deadline, the ministers are racing to resolve a handful of stubborn disputes that have blocked the path to a universal climate pact for more than 20 years.

French Foreign Minister Laurent Fabius, presiding over the conference, said he would deliver a streamlined draft for the deal by 1pm (1200 GMT) Wednesday, after receiving feedback from splinter groups haggling over the tough issues.

"It will be an important step, I hope, but not yet the final result," he said.

Nations remain divided over how to help developing nations cope with the costs of global warming, what limit to set for planetary overheating, how to share the burden between rich and poor nations and how to review progress in slashing greenhouse gases.

"Though we have some tough issues in the next few days to resolve I am confident that we have the ability to do it," US Secretary of State John Kerry said on the sidelines of the conference at Le Bourget on the northern outskirts of Paris.

- 'Dirty work' -

"They are finally doing the dirty work of negotiating, which is very hard," said Jennifer Morgan, climate analyst at the Washington-based World Resources Institute, an observer at the talks.

"You are finally starting to see the really hard bargaining and arguing that has to happen. It is a good thing, because otherwise they would still be standing by their positions."

Observers said a new sense of confidence was emerging in Paris, a hopeful sign six years after the spectacular collapse of the last attempt to reach a global deal in Copenhagen, fractured by distrust between rich and poor countries.

"I believe we can find a comprehensive, ambitious, legally binding agreement with no person left behind. I'm fully confident," said China's top climate negotiator Xie Zhenhua.

India's environment minister, Prakash Javadekar, said he was disappointed by a "low level of ambition" among rich nations, but predicted the world was "roughly 80 hours away" from a deal.

"The Paris agreement is going to be a reality," declared Brazil's environment minister, Izabella Teixeira.

Taking effect in 2020, the Paris agreement would seek to limit emissions of heat-trapping greenhouse gases driven by burning coal, oil and gas -- the backbone of the world's energy supply today.

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

- 'Receiving the punches' -

Negotiations are making headway on every front, said France's top negotiator, Laurence Tubiana. "We are advancing on everything," she said. "There is no issue where we are blocked. None."

One if the biggest potential deal-busters is money.

Rich countries promised in 2009 to muster $100 billion (92 billion euros) a year from 2020 to help developing nations make the costly shift to clean energy, and to cope with the impact of global warming.

But how the pledged funds will be raised remains unclear -- and developing countries are pushing for a promise that the amount will be ramped up beyond 2020.

Meanwhile, rich nations are insisting that developing giants work harder to tackle their greenhouse gases, noting that much of the world's emissions come from their fast-growing economies.

Singapore's foreign minister, Vivian Balakrishnan, cautioned that "faultlines remain" over how to share greenhouse gas cuts between rich and developing nations.

Small island states at risk of being swamped by higher seas are pushing for a lower warming ceiling of 1.5C.

"We are the face of vulnerability," said Philippines' climate delegate and leader of the bloc of vulnerable nations, Emmanuel de Guzman.

"We've been absorbing the punches and we will continue to receive these punches as the planet continues to warm."

- 'Tame this monster' -

Nevertheless, he said, countries most at risk could accept a deal with 2C as the formal goal, as long as it makes a reference to the lower 1.5C threshold.

"I hope the parties will accelerate the speed of their negotiation so that by Friday evening we will have a universal and robust climate change agreement," UN Secretary General Ban Ki-moon said in Paris.

Warning of the price of inaction, Kerry said the United States spent $126 billion last year undoing the damage of eight huge storms.

The top US diplomat described the splintered wood he had seen strewn across the mountains of the Philippines in the path of Typhoon Haiyan that struck in November 2013, leaving more than 7,350 people dead or missing.

"That's the future, folks, unless we tame this monster that we have unleashed," he said.

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