Le Bourget -Developing nations warned Wednesday that a bitter row over money was threatening efforts to seal a historic pact to tame global warming, as the French hosts pleaded for compromise.
The UN-brokered talks involving 195 nations are facing a tight deadline of December 11 to forge an agreement aimed at cutting the greenhouse gases blamed for climate change, and averting its catastrophic impacts.
But despite more than 150 world leaders opening the talks on Monday with lofty rhetoric about the urgency of the task, bureaucrats became quickly ensnared in familiar rows that have condemned previous efforts to failure.
"My message is clear: we must accelerate the process because there is still a lot of work to do," said French Foreign Minister Laurent Fabius, who is presiding over the negotiations.
"Options for compromise need to be found as quickly as possible."
One of the most fiercely contested issues in the 25-year diplomatic effort to find a solution to global warming has been how much responsibility rich nations must accept for the problem, and therefore how much they should pay.
The United States and other developed countries have powered their way to prosperity since the Industrial Revolution by burning coal, oil and gas, which is the primary cause of the heat-trapping greenhouse gas emissions.
Developing nations insist the developed ones must now largely finance the world economy's costly shift away fossil fuels, a debate worth hundreds of billions of dollars.
A powerful bloc of 134 developing nations, including China, India and all African and South American countries released a statement near the end of Wednesday's negotiations insisting the rich were again trying in Paris to absolve themselves of their financial responsibilities.
"Nothing... can be achieved without the provision of means of implementation to enable developing countries to play their part to address climate change," the statement said.
The bloc, known as the G77 plus China, restated a demand for rich nations to follow through on their commitment to mobilise $100bn a year into a climate change from 2020.
It also demanded as "substantial scaling up of finance" on top of the previously agreed $100bn.
The financing issue is central to hugely complex 54-page draft text that negotiators need to trim down by the weekend, so that ministers have a week to try and finalise it.
Frustration permeated the negotiating halls of the convention centre in the northern outskirts of Paris on Wednesday.
"We are not making anywhere near the progress we need to be making at this point," said Daniel Reifsnyder, one of the two co-chairmen in the talks' key arena.
Greenpeace climate campaigner Li Shuo, who has observer status in the talks, described them as "quite messy".
"At some point, we definitely need to switch gear," he said.
Still, such frustrations are typical of the start of climate negotiations, where vast interests are at stake and a single word in an agreement can have big repercussions, said veteran observers.
Wealthy climate villains
"I remain confident that it will be a hard fought two weeks but at the end of the day we are likely to achieve, and I believe we will achieve, an agreement," Australian Environment Minister Greg Hunt told reporters.
UN climate chief Christiana Figueres cautioned against despair.
"The text of the agreement will go through ups and downs, there will be many commas inserted and commas removed because that is the nature of this. It is a legally binding text and needs to be reviewed very, very carefully," she said.
Touching on the rich-poor issue, British charity Oxfam issued a study saying the wealthiest 10 percent of people produce half of Earth's fossil-fuel emissions, while the poorest half contribute a mere 10 percent.
An average person among the richest one percent emits 175 times more carbon than his or her counterpart among the bottom 10 percent, the charity said.
At the core of the talks is the goal of limiting warming to a maximum of two degrees Celsius over pre-Industrial Revolution levels.
That objective, along with a more ambitious option of 1.5 C has been enshrined in the UN Framework Convention on Climate Change (UNFCCC) since 2010.
Since then, scientists have pounded out an ever-louder warning that relentlessly climbing carbon emissions will doom future generations to rising seas and worsening floods, storms and drought, a recipe for hunger, disease and homelessness for many millions.