UN Secretary-General Antonio Guterres has urged rich countries to deliver the promised $100 billion a year for climate action in developing countries.

Addressing reporters on Monday at the UN headquarters in New York following the closing of the Informal Leaders Roundtable on Climate Action, he said: "Today, I asked leaders to do what is needed to make sure COP26 is a success and that it marks a true turning point.

"Developed nations need to implement their promise to mobilise $100 billion dollars a year for climate action in the developing world from 2021 to 2025.

"We failed in 2019 and 2020. OECD (the Organization for Economic Cooperation and Development) calculations say we are about $20 billion short.

"Failure to fulfil this pledge would be a major source of the erosion of trust between developed and developing countries. Developed nations need to bridge this gap." On the current climate change situation, the UN chief said that "to limit temperature rise to 1.5 degrees, we need a 45 per cent cut in emissions by 2030 so we can reach carbon neutrality by mid-century", reports Xinhua news agency.

"Instead, the commitments made until now by countries imply an increase of 16 per cent in greenhouse gas emissions -- not a decrease of 45 per cent -- an increase of 16 per cent in greenhouse gas emissions in 2030 compared to 2010 levels," he warned.

Guterres said that "the Intergovernmental Panel on Climate Change says that the 1.5-degree goal is still in reach. But we need a dramatic improvement in Nationally Determined Contributions from most countries". On energy, the Secretary-General said that "governments must shift subsidies away from fossil fuels and progressively phase out coal use".

"If all planned coal power plants become operational, we will not only be clearly above 1.5 degrees, we will be well above 2 degrees. The Paris targets would go up in smoke," said the UN chief.

Guterres and UK Prime Minister Boris Johnson on Monday held the closed-door Informal Climate Leaders Roundtable on Climate Action with a small but representative group of heads of state and government, on the sidelines of the General Assembly.

The roundtable follows the recent report of the Intergovernmental Panel on Climate Change, signaling a "code red for humanity," and comes less than six weeks before the COP26 Climate Change Conference in Glasgow from October 31 to November 12. The roundtable addresses the gaps that remain on the actions urgently needed from national governments, especially the G20, on mitigation, finance and adaptation.