France has signalled a "breakthrough" at 46-nation talks in Paris tasked with paving the way for a highly-anticipated climate rescue pact to be inked in December.
Ministers and top officials at an informal gathering on Tuesday (local time) have reached consensus on several issues that have stymied the official negotiations for years, France's top climate negotiator Laurence Tubiana told journalists.
Crucially, they have agreed there should be a regular five-yearly review once the agreement kicks in, of the collective effort to curb planet-warming greenhouse gases.
"This is a breakthrough," said Tubiana. "That was not obvious to get."
The political signal emerging from the Paris talks will now filter down and hopefully ease the job of rank-and-file negotiators for the 195 countries crafting a historic global agreement.
The Paris talks were not part of the official negotiations, and fewer than a quarter of countries were directly represented.
But all the world's top greenhouse gas emitters, apart from Russia, were represented, as were all recognised negotiating blocs.
Foreign Minister Tony de Brum from the Marshall Islands, one of the small island states at highest risk of climate change-induced sea level rise, welcomed the progress.
"The French initiative to engage ministers early and often is a clever one. It's a move that will help to ensure success in Paris," he told AFP.
"The process needs a political nudge. Having ministers talking to each other, sitting around eye-to-eye,that helps to move things along."
The pact to be finalised at a December UN conference in Paris will aim to limit average global warming to 2degC over pre-Industrial Revolution levels.
It will be supported by a roster of voluntary national pledges. But scientists say that those already submitted indicate the world will badly miss the 2degC target which is considered the threshold for disastrous impacts.