PARIS - France’s top diplomat, who will preside over a year-end Paris summit tasked with inking a global pact to rein in global warming, warned Sunday of a looming planetary “catastrophe”.

With the key UN conference just three weeks away, Foreign Minister Laurent Fabius also announced that Russia’s President Vladimir Putin would attend the November 30 opening.

Russia, a major oil producer, is seen as a deal-maker or breaker in the years-long attempt to negotiate the world’s first truly universal pact to rein in global warming by curbing climate-altering greenhouse gas emissions.

“It is life on our planet itself which is at stake,” Fabius told journalists as ministers and climate envoys from 70 countries met in the French capital for pre-summit talks to iron out tough political questions.

“There is absolute urgency,” he added, in chasing the UN goal of limiting global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.

The UN’s climate science panel has warned of an average temperature rise of “four, five, six degrees, if we do not act extremely quickly,” said Fabius.

“This would have catastrophic consequences because there would be drought... and colossal migration problems, including problems of war and peace.”

The three-day ministerial gathering, from Sunday to Tuesday, must seek political convergence on key political issues still dividing nations negotiating for a climate pact. It is meant to be inked by ministers at the end of a November 30-December 11 UN summit, crowning years of tough bartering.

That meeting is set to be opened by UN chief Ban Ki-moon and some 100 heads of state and government including US President Barack Obama, China’s Xi Jinping, Narendra Modi of India and now Putin.

The Paris agreement will be the first uniting all the world’s nations in curbing climate-altering greenhouse gas emissions from burning coal, oil and gas. But the UN this week issued a fresh warning that country pledges submitted to date set the stage for warming of closer to 3 C, or more. Ministers will base their discussions in the coming days on a rough draft of a deal compiled by rank-and-file diplomats over years of tough negotiations in the UN climate forum.

The blueprint remains little more than a laundry list of often directly-opposing national options for dealing with the challenge at hand. The last round of technical negotiations in Bonn in October saw squabbles along well-rehearsed fault lines of developed vs developing nations.

Developing countries insist rich ones should lead the way in slashing emissions because historically they have emitted more pollution.

Developing nations also want assurances of financing to make the shift from cheap and abundant fossil fuel to more sustainable energy sources, and to shore up defences against climate change-induced superstorms, drought, flood and sea-level rise.

But industrialised countries point the finger at emerging giants such as China and India spewing carbon dioxide as they burn coal to power expanding populations and economies.

These crux issues must ultimately be settled at the political level - by ministers and heads of state and government.

The preparatory brings together ministers of all the negotiating blocs, and includes top envoys from major carbon emitters China, the United States, the European Union, India, and Brazil. It is the third such ministerial round in Paris this year.

Much work lies ahead outside the 195-nation UN climate forum, including a G20 summit in Turkey this month where the thorny issue of climate finance will be discussed. Last month, scientists said the first nine months of 2015 had been the hottest on record worldwide.