Ministers from around the world have been set to work on securing a new global climate deal as the high level part of crucial United Nations talks in Paris begin.
The second week of the talks start after negotiators agreed a draft of the deal, which aims to curb temperature rises and avoid dangerous climate change, over the weekend - though there are still major sticking points.
Key issues that need to be thrashed out include a long-term goal for reducing the emissions that cause dangerous climate change by the second half of the century and the provision of finance for poor countries to cope with global warming.
The president of the "COP21" talks, French foreign minister Laurent Fabius, has brought the negotiations together under the so-called "Paris Committee" to make progress and facilitate compromises between the 195 countries negotiating the agreement.
Groups led by ministers will cover areas including implementing support for countries to tackle climate change, how to differentiate between rich and poor countries in the action they will take, and the ambition of the treaty including a long term goal to cut emissions and periodically reviewing progress.
The UK's Energy and Climate Change Secretary Amber Rudd and the Gambia's environment minister Pa Jarju Ousman will lead a group looking at increasing the action countries will take to curb emissions before 2020, when the Paris deal would kick in.
Ms Rudd said: "I am hopeful that we can get a deal, but I am not complacent.
"As one of eight ministers from around the world asked by the COP 21 Presidency to help facilitate the deal, I am clear that there is a huge amount of work to get through.
"Compromises and some hard decisions will need to be made, by all of us."
The French have set a tough timetable, wanting a final draft of the deal by Thursday - but experience from previous negotiations suggests the talks will overrun their official finish on Friday.
Ahead of the high-level segment of the talks, WWF UK's chief executive David Nussbaum urged Ms Rudd to show leadership, in solidarity with those countries already affected by climate change.
He said: "Now ministers have arrived in Paris, we enter the final straight. There is still much to do and the stakes are high.
"We need a fair, ambitious and transformational deal by Friday.
"The negotiations over the last week in Paris reflect the combined will of nearly 200 countries. At the moment, the text still includes the varying preferences of all the countries. In the coming days, Ministers must build consensus on the remaining sticky issues.
"But as things stand, the Prime Minster was right in his opening speech here in Paris: this is doable."
UN secretary general Ban Ki-moon said he was optimistic and confident that the talks would conclude with a universal and ambitious agreement, as he urged countries to look beyond their national boundaries to secure a deal on climate change.