Brazil said Friday it had joined the European Union, United States and 79 developing nations in a group calling for a far-reaching deal at UN climate-saving talks in Paris.

The informal "high ambition coalition", announced by the European Union during the 195-nation conference in Paris this week, includes more than half of the countries of the world but is not a formal negotiating bloc.

Nevertheless, the alliance is calling for a legally binding, fair, durable agreement in Paris that must set a long-term goal, be reviewed every five years and include a system for tracking progress.

Brazil is the first major emerging economy to join the group.

"If you want to tackle climate change, you need ambition and political will," Brazil's Foreign Minister Izabella Teixeira said in a statement.

"Brazil proudly supports the high ambition coalition and pledges our political support to this effort."

As the talks in Le Bourget on the northern outskirts of Paris lurch into overtime, decisions taken on a handful of core issues may determine whether it is seen as being up to the task of tackling climate change.

The latest draft accord, still open to change, says its purpose is to hold temperatures to well below two degrees Centigrade (3.6 degrees Fahrenheit) above pre-Industrial Revolution levels. But it also says nations should aim for 1.5C, a target backed by the new grouping.

The world will aim for climate-altering greenhouse gas emissions to peak "as soon as possible", the draft accord says. Countries would then make rapid cuts to reach "greenhouse gas emissions neutrality" -- the point at which the level of heat-trapping gases in the atmosphere stabilises -- in the second half of this century.

Other key issues yet to be decided include how often to review and strengthen national carbon gas-cutting pledges, and when to start doing so.

Among the major players absent from the so-called high ambition coalition are India and China. India in particular has balked at moving toward the higher end of the spectrum on all these goals.

However, the "high ambition coalition" members are not united on some key points, including on how the rich nations should mobilise finances for the developing world to pay for the cost of climate change.

"This move by Brazil could change the whole dynamic in the last closing hours of this conference," said Greenpeace analyst Martin Kaiser. "Missing from the coalition were any of the major emerging economies."