US Secretary of State John Kerry said the USA supports the "high ambition coalition" aiming for a strong deal to tackle climate change.
Speaking two days before the end of the UN Climate Change Conference in Paris, Kerry called for an ambitious deal that would not set the "ceiling" but only "build the floor" for future global warming mitigation efforts.
“We need an agreement that is as ambitious as possible," Kerry said. "Unless the global community takes bold steps now to transition away from high carbon... we are facing unthinkable harm to habitats, infrastructure, food production, water supplies and potentially to life itself.”
He expressed support for a group of 79 African, Caribbean and Pacific countries and the European Union, which announced yesterday their goal to see a legally binding, ambitious and fair deal that would set out long-term targets reflecting current scientific knowledge about climate change.
The coalition, which makes up for more than half the countries present at the talks, wants to see reviews of progress conducted every five years to assess how individual nations are delivering on their promises.
Raising ambitions regarding progress, the countries believe, is key to limiting the increase of average global temperatures to the 2°C deemed necessary by climatologists to prevent excessively adverse effects on the ecosystem, as well as society.
In fact, some countries even supported a more ambitious goal of 1.5°C. According to current projections, existing policies would only limit the temperature rise to 3°C.
In his speech, Kerry also called for a review and ratchet system in the deal to increase emissions cuts by countries over time.
A draft agreement was released on Wednesday which has left many controversial questions still unresolved.
The 29-page document doesn’t say whether the long-term goal is to remove carbon emissions altogether or merely reduce them.
The question over whether the aim should be to limit the temperature rise to 2°C or 1.5°C compared to pre-industrial times has also been left unanswered.
There are about 100 places where there are decisions still to be made; either multiple options in brackets or simply blank spaces.
French Foreign Minister Laurent Fabius said "three-quarters" of the brackets in the previous version have been deleted, meaning negotiators have come to agreement on a number of the myriad sticking points.
These include how to define the obligations of countries in different stages of development in fighting climate change. Developing nations such as India believe that established Western nations - who largely grew wealthy during periods of heavy pollution, such as the Industrial Revolution - should shoulder the burden of the mitigation efforts now, allowing developing nations more time to catch up.