"Let's get to work" - it was with this appeal that US President Barack Obama ended his statement after talking for almost 14 minutes, oblivious to a horn honking to indicate that his allotted time of three minutes had run out.

Obama said he had come personally as representative of the world's second largest emitter of greenhouse gases to let the world know "that we are embracing our responsibility to do something" about climate change.

The president announced that the US would make new financial contributions to the Least Developed Countries Fund and called on other leaders to "make sure that resources flow to countries that need help."

'In your hands'

Obama's appeal came almost two hours after French President Francois Hollande and UN Secretary-General Ban Ki-moon formally opened the conference.

Hollande admonished fellow leaders that this time around, saying that "declarations of intention" were not going to be enough. Paris, he said, needed to conclude with an agreement that was "binding, universal and differentiated."

"The fate of a Paris agreement rests with you," Ban told the world leaders gathered at the Le Bourget conference site. "The future of our planet is in your hands."

Merkel: Review of pledges needed

German Chancellor Angela Merkel stressed that the agreement to be negotiated in Paris had to be "ambitious, fair and binding."

The pledges made so far by various nations to reduce emissions are still insufficient to limit global warming to 2 degrees Celsius (3.6F) - the goal set by the international community at previous conferences. In light of this Merkel said there had to be a regular stocktaking of emissions and actions. No country should be allowed to backtrack on its pledges, Merkel said.

"There has to be clear transparency in how emissions are measured," Merkel said, outlining clearly what Germany and the European Union sought in the negotiations.

In saying that "far-reaching" decarbonization of the global economy was needed by the end of the century, however, Merkel appeared to water down a statement put forth at a summit of the seven world's biggest economies earlier this year.

Then, the leaders hosted by Merkel in Elmau, Germany, had stated that decarbonization of the global economy was needed - without the qualifying adjective "far-reaching."

Merkel's modification could be construed to signal compromise to countries that, like India, have stated objections to using the phrase "decarbonization."

Xi endorses autonomy

Notwithstanding appeals for consensus and compromise, many leaders' statements hinted at the differences that will need to be reconciled before a universal climate treaty can be agreed.

For his part, Chinese President Xi Jinping put the emphasis on calling on developed countries to honor their financial commitments to assist developing nations as they embark on low-carbon growth paths.

Developing countries should "not be denied legitimate rights" to grow, Xi said, adding that it was "imperative to respect differences among countries."

"The principle of common but differentiated responsibilities should be adhered to," he said, referring to a tenet of the in the UN Framework Convention on Climate Change.

"Countries should be allowed to seek their own solutions," Xi said.