Donald Trump's election loomed large over climate talks on Tuesday where UN chief Ban Ki-moon urged nations to redouble their planet-rescue efforts and voiced hope the US would not pull out of its commitments.

Elected to the White House a week ago, Trump has called global warming a "hoax" perpetrated by China and threatened to "cancel" the hard-fought Paris Agreement concluded a year ago.

Ban said he had spoken to the businessman turned president-elect, and was "optimistic" Trump "will hear and understand the seriousness and urgency of addressing climate change".

"As the president of the US I am sure he will understand this, he will listen, he will vary his campaign remarks," the outgoing UN secretary general told journalists.

"I am sure he will make a good, wise decision."

Gathered in Marrakesh since last Monday, representatives from the UN climate body's 197 parties have started designing a roadmap for putting the agreement into action.

But Trump's ascension to the US presidency has been uppermost on the minds of delegates and negotiators.

Many fear that withdrawal by the United States, a champion of the deal under Barack Obama, would shatter the political goodwill built up over years of negotiations, and place the very goals of the deal at risk.

Ban joined some 80 heads of state and government for a "high-level segment" of the annual UN climate meeting -- the first since last year's adoption of the Paris Agreement to stave off worst-case-scenario global warming.

President Francois Hollande of France, which hosted last year's deal-clinching climate huddle, insisted the United States "must respect the commitments it has undertaken."

"It is not only their duty, it is in their interest as well as (the interest of) all people," he told the gathering.

Taneti Maamau, the president of the island nation of Kiribati, agreed Washington had an "important role" to play.

"We are now faced with the biggest challenge of our time and we look to the US to continue their leadership," he told the gathering.

- Gambling on the future -

The Paris pact sets out the objective of limiting average global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels by cutting planet-heating greenhouse gases from burning coal, oil, and gas.

Leaders of African nations and island states at high risk of an altered climate, urged rich nations to do more to cut emissions and to ramp up climate finance.

"Developed countries must shoulder their historical responsibility for emissions," said President Ismail Omar Guelleh of Djibouti.

"Implementation of the Paris Agreement is subject to mobilisation, availability and direct accessibility of adequate financial resources by developed countries for developing countries," he said.

The UN, too, called for more money, especially for "adaptation" -- shoring up defences against global warming's effects.

This could mean building dykes or elevating homes as protection against rising seas, improving weather warning systems and growing climate change-resistant crops.

Less than a fifth of climate funding goes to adaptation today. The bulk is to help developing countries make the costly shift from fossil fuels to greener energy sources -- called "mitigation" in UN climate jargon.

Rich nations had pledged 2009 to mobilise $100 billion (93 billion euros) per year from 2020 in overall climate aid.

But the UN's environment organ, UNEP, said as much as $300 billion may be needed by 2030 for adaptation alone, and up to $550 billion by 2050.

"When we as developing countries call for priority to be accorded to adaptation... we do so because it is a matter of life and death," Zimbabwe's President Robert Mugabe told the meeting.

"A dead person cannot mitigate for climate change."

To date, 110 of 197 parties to the UN's climate convention have ratified the Paris Agreement, which entered into force on November 4.

They included the US, but Trump can withdraw Washington from the deal.

While waiting for the new president to make his position clear, many now look to the rest of the world to strongly restate their commitment to the agreement, with or without the US.

Ban urged signatories Tuesday to raise the non-binding pledges they had made to curb carbon emissions, saying commitments as they stand "will not get us out of the danger zone."

He also called for the elimination of fossil fuel subsidies, estimated at more than $500 billion (465 billion euros) a year.

Last year was the warmest on record, and 2016 was on course to be hotter still, Ban, whose term ends in December, said at his tenth and final climate conference as UN chief.

"We have no right to gamble with the fate of future generations or imperil the survival of other species that share our planet," he said.