G20 countries should show leadership by keeping the 1.5 degrees Celsius goal alive, rebuilding trust based on climate justice and advancing just and equitable transition through a green economy, United Nations General Secretary Antonio Guterres said on Friday.

Antonio Guterres said G20 leaders have the power to reset a climate crisis that is "spinning out of control" and urged them to reshape global financial rules which he described as outdated and unfair.

At the Paris climate talks in 2015, countries agreed to limit global warming to 1.5 degrees Celsius as compared to pre-industrial levels (1850-1900) to avoid extreme, destructive and likely irreversible effects of climate change.

"We have no time to lose, challenges stretch as far as I can see. The climate crisis is worsening dramatically but the collective response is lacking in ambition, credibility and urgency," Guterres told a press conference on the eve of the G20 Summit here.

He urged the G20 countries -- responsible for 85 per cent of the world's GDP and 80 per cent of the emissions -- to demonstrate leadership in two priority areas: preventing a climate breakdown and saving the sustainable development goals.

"The climate crisis is spiralling out of control, but G20 countries are in control. Together, G20 countries are responsible for 80 percent of global emissions. Half measures will not prevent full climate breakdown," he said.

Guterres urged the G20 leaders to keep the 1.5 degrees Celsius goal alive, rebuild trust based on climate justice and advance just and equitable transition through a green economy.

He urged big emitters to make extra efforts to cut emissions and support emerging economies to achieve these.

He said developed countries should reach net zero by 2040 and the emerging economies by 2050.

OECD countries should phase out coal by 2030 and the others by 2040, he added.

The UN chief said the developed countries within the G20 should show leadership by delivering on commitments to developing countries, by meeting the USD 100 billion goal, doubling adaptation finance, replenishing Green Climate Fund and operationalising the loss and damage fund created in the last Conference of Parties to the United Nations Framework Convention on Climate Change (UNFCCC).

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