Ministers from around the world have worked through the night as the talks for a new deal on climate change enter their final days.
Efforts are being made to break divisions on key issues in the agreement which aims to avoid dangerous climate change and provide finance for poor countries to deal with the impacts of global warming.
A draft of the text for the agreement released on Wednesday contained the potential for ambitious targets on curbing rising global temperatures and cutting emissions over the coming decades, as well as weaker options, and a new text is expected later today.
The "high ambition coalition" of countries including the EU, some of the world's poorest countries and the US, are calling for a robust "review and ratchet" mechanism in the deal that would see countries re-examining and raising their level of pledged climate action if appropriate every five years.
Making sure ambition can be raised is key to achieving a 2C limit to global temperature rises - beyond which "dangerous" climate change is expected - or the more stringent 1.5C many countries have backed.
This is because the current pledges by countries for climate action they will take up to 2030 will only put the world on a path to almost 3C.
The issue of "differentiation" - the difference between the responsibilities and action of different countries - also remains a thorny issue in the discussions, as does finance for poor countries, and the "loss and damage" question over support for countries suffering irreversible consequences of rising temperatures.
Some countries, thought to include China and India, are trying to maintain the UN climate convention's original strict split between developed and developing countries laid down in 1992, while others such as Europe are seeking wording that reflects the range of countries' development and their ability to act.
Campaigners are calling for a strong deal that protects the most vulnerable people in the world.
Samantha Smith, leader of WWF's global climate and energy initiative, said: "There's a debate now of whether the upper limit for temperature should be 1.5C or 2C, this is a critical difference, it's a difference for people's lives, for some of the most important ecosystems in this world and communities that rely on them.
"But the temperature target is not enough because we don't see the emissions reductions, the finance, the technology access on the table from developed countries that would enable us to together meet this challenger of climate change."
Kumi Naidoo, executive director of Greenpeace International urged leaders: "Stop political poker playing with the future of our children and their children in the last 24 hours or so of these negotiations."