Countries come to Baku after new warnings that 2024 is on track to break temperature records, adding urgency to a fractious debate over climate funding.

"We are on a road to ruin," Babayev warned at the start of the two-week conference in Azerbaijan's capital, pointing to recent deadly floods in Spain and other climate catastrophes.

Trump has pledged to once again withdraw the United States from the landmark Paris agreement, which set the ambitious goal of limiting warming to 1.5 degrees Celsius above pre-industrial levels.

"COP29 is a moment of truth for the Paris agreement," said Babayev.

"It will test our commitment to the multilateral climate system. We must now demonstrate that we are prepared to meet the goals we have set ourselves," he added.

The conference must find common ground on increasing a $100 billion-a-year target in funding for developing nations to manage climate impacts and wean their economies off fossil fuels.

- 'Trillions needed' -

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

Developing countries are pushing for trillions of dollars, and insist money should be mostly grants rather than loans.

"We know the needs are in the trillions, but there are different views on how to achieve that," Babayev said.

"We have also heard that a realistic goal for what the public sector can directly provide and mobilise seems to be in the hundreds of billions," he said.

Azerbaijan's ecology minister and a veteran of its state oil company SOCAR, Babayev said negotiations were "complex and difficult".

"We understand the political and financial constraints," he added.

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

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.

That is firmly rejected by Beijing.

"The COP29 presidency has made every effort to bring the parties closer together," Babayev said.

"But we still have much to do and just 12 days to land a deal. We now urgently need to finalise the elements, resolve our differences on contributors and quantum, and set the new goal."