Washington's top climate envoy sought to reassure countries at the COP29 talks Monday that Donald Trump's re-election would not end US efforts to tackle global warming.

Trump's sweep of the presidential vote has cast a long shadow over the crunch talks in Baku, with the incoming US leader pledging to withdraw Washington from the landmark Paris climate agreement.

The vote has left the US delegation somewhat hamstrung and stoked fears other countries could be less ambitious in a fractious debate on increasing climate funding for developing nations.

US envoy John Podesta acknowledged the next US administration would "try and take a U-turn" on climate action, but said that US cities, states and individual citizens would pick up the slack.

"While the United States federal government under Donald Trump may put climate change action on the back burner, the work to contain climate change is going to continue in the United States with commitment and passion and belief," he said.

"The fight is bigger than one election, one political cycle in one country."

The Baku talks opened earlier Monday with UN climate chief Simon Stiell urging countries to "show that global cooperation is not down for the count."

Things got off to a rocky start, with feuds over the official agenda delaying by hours the start of formal proceedings in the stadium venue near the Caspian Sea.

But in the evening, governments approved new UN standards for a global carbon market in a key step toward allowing countries to trade credits to meet their climate targets.

COP29 president Mukhtar Babayev hailed a "breakthrough" after years of complex discussions but more work is needed before a long-sought UN-backed market can be fully realised.

'Climate debt'

The main agenda item at COP29 is increasing a $100 billion-a-year target to help developing nations prepare for worsening climate impacts and wean their economies off fossil fuels.

How much will be on offer, who will pay, and who can access the funds are some of the major points of contention.

Babayev acknowledged the need was "in the trillions" but said a more "realistic goal" was somewhere in the hundreds of billions.

"These negotiations are complex and difficult," the former executive of Azerbaijan's national oil company said at the opening of the summit.

Developing countries warn that without adequate finance, they will struggle to offer ambitious updates to their climate goals, which countries are required to submit by early next year.

"The global North owes the global South a climate debt," said Tasneem Essop, executive director of Climate Action Network.

"We will not leave this COP if the ambition level on the finance... doesn't match the scale at which finance must be delivered."

Stiell warned rich countries to "dispense with any idea that climate finance is charity."

"An ambitious new climate finance goal is entirely in the self-interest of every nation, including the largest and wealthiest," he said.

'Great peril'

The small group of developed countries that currently contributes the money wants the donor pool expanded to include other rich nations and top emitters, including China and the Gulf states, something firmly rejected by Beijing.

Just a handful of leaders from the Group of 20, whose countries account for nearly 80 percent of global emissions, are attending. US President Joe Biden is staying away.

Afghanistan is however present for the first time since the Taliban took power, as guests of the host Azerbaijan but not party to the talks.

The meeting comes after fresh warnings that the world is far off track to meet the goals of the Paris agreement.

The UN said Monday that 2024 is likely to break new temperature records, and the Paris climate agreement's goals were now "in great peril".

The period from 2015 to 2024 will also be the warmest decade ever recorded, the UN's World Meteorological Organization said in a new report.

The climate deal commits to keep warming below 2 degrees Celsius compared to pre-industrial levels, preferably below 1.5C.

If the world tops that level this year, it would not be an immediate breach of the Paris deal, which measures temperatures over decades.

But it suggests much greater climate action is needed.

Last month, the UN warned the world is on a path towards a catastrophic 3.1C of warming this century based on current actions.

More than 51,000 people are expected at COP29 talks, which run from November 11 to 22.