Canada has endorsed a call from small island nations to hold global warming to no more than 1.5 degrees Celsius above pre-industrial levels, putting Ottawa out of step with the United States, which has maintained a 2 C target.

In a closed-door session Sunday, Environment Minister Catherine McKenna said the 1.5 C goal should be reflected in the final accord, though the United Nations has said the emissions-reduction commitments from countries attending the Paris climate summit would fall well short of what is needed to achieve even the 2 C limit.

The Environment Minister's backing of the aggressive global-warming goal marked a sharp departure from the position of the Harper government.

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Ms. McKenna said the 2 C threshold should be a minimum ambition that countries endorse, but any agreement should also reflect the concern that that level of warming would have dire consequences for many nations.

Her citing of the 1.5 C target is consistent with the European Union.

Green Party Leader Elizabeth May – who attended the meeting as a Canadian delegate – characterized Ms. McKenna's intervention as "fantastic," saying the minister endorsed the need for a five-year review of any Paris agreement as well as the inclusion of language of indigenous and human rights.

Island nations have pleaded with the 195 countries at the Paris climate conference to hold global warming to 1.5 C, saying a higher temperature would doom their low-lying lands to inundation from rising seas and force mass relocations.

On Friday, U.S. chief negotiator Todd Stern said the concerns of small island states are legitimate and the United States is "exploring appropriate ways to address their concerns."

After a week of negotiations, environment and foreign ministers arrived Sunday, with the aim of concluding a deal by Friday. Deep divisions remain on some key issues, including financing and the level of commitment required by large emerging economies such as China and India.

There were high hopes that those disagreements would not doom the talks to failure. "I am optimistic and confident that we will have a universal and ambitious agreement," United Nations Secretary-General Ban Ki-moon said on Sunday.

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The optimism reflects the completion of a 48-page draft agreement, whittled down from a 55-page draft, that was submitted by negotiators from 195 countries on Sunday. While the agreement contains numerous pitfalls, negotiators and environmental groups said the progress so far was a notable improvement over the first week of negotiations at the Copenhagen conference in 2009, which ended in failure.

On Sunday, French Foreign Minister Laurent Fabius appointed Ms. McKenna as a facilitator in the Paris negotiations. In her role, she will lead informal discussions among her counterparts to help bridge some of the gaps in the negotiating text.

The gruelling negotiations over financing – the big ticket item in Paris – come as no surprise. The developing world countries are demanding clear indications on how wealthy countries intend to finance $100-billion (U.S.) a year in climate-change adaptation and mitigation measures by 2020.

The figure, from both public and private sources, was set at the Copenhagen conference and has met with incomplete success. The Organization for Economic Development and Co-operation estimated the rich countries "mobilized" some $62-billion in 2014 for climate efforts in the developing world, though the recipient countries argue the true figure is considerably less.

"It's the same issue that is rearing its head again," Dale Marshall, national energy program manager of Toronto's Environmental Defence, said Sunday. "The developing world is looking for predictable levels of financing and they want to see a pathway to $100-billion."

The biggest countries in the developing world, among them China, India and Malaysia, are adamant the new accord should respect a fundamental principle set out in the Kyoto Accord – that countries have common but differentiated responsibilities. In essence, the principle recognizes that all countries have responsibility to bring down carbon emissions, for the sake of the health of the planet, but that the industrialized world, which built its wealth on burning fossil fuels with abandon, has an enormous obligation to help to protect the developing world from climate change.

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Developing countries are also nervous the United States may not deliver the promised funding because Republicans in Congress are vowing to block budget appropriations for international climate assistance. The administration of U.S. President Barack Obama opposes a legally binding accord in Paris because it fears that Congress would block any deal that legislates payments to the developing world.

Climate consultant John Drexhage, who is a former negotiator on the Canadian climate team, said the principle of common but differentiated responsibilities is permeating all the talks in Paris, not just financing. "I would say that this is at the core of the key outstanding issues, including financing, more stringent and absolute emissions targets for developed countries, the monitoring, reporting and verification mechanisms for emissions and the legal nature of the agreement," he said.

On Monday, Premiers Kathleen Wynne of Ontario, Philippe Couillard of Quebec and Christy Clark of British Columbia will be in Paris to highlight the efforts their provinces have made to reduce carbon emissions.

Editor's note: An earlier digital version of this story incorrectly quoted John Drexhage when he referred to more stringent and absolute emissions targets. He was referring to developed countries, not developing ones. This digital story has been corrected.