UN Secretary-General 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climate crisis that is "spinning out of control" and urged them to reshape global financial rules which he described as outdated and unfair.

"The climate crisis is worsening dramatically – but the collective response is lacking in ambition, credibility, and urgency," Guterres said in a speech in New Delhi, capital city of India, which is chairing the G20 this weekend.

Guterres asked the G20 to commit to keeping the "1.5 degree goal alive" - referring to the 2015 Paris Agreement goal of limiting the global average temperature rise to well below 2°C above pre-industrial levels, and aiming for 1.5°.

"I have put forward a Climate Solidarity Pact – in which big emitters make extra efforts to cut emissions; and wealthier countries support emerging economies to achieve this," Guterres said.

The plan urges developed countries to reach net-zero as close as possible to 2040, and emerging economies as close as possible to 2050, proposing a phase out of coal by 2030 in the Organization for Economic Co-operation and Development (OECD) countries and 2040 in all others.

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

The UN chief also called on G20 leaders to ensure a stimulus of at least $500 billion per year towards meeting the Sustainable Development Goals.

An effective debt workout mechanism is needed to support payment suspensions, longer lending terms and lower rates on fairer terms for poorer countries, he said.

Calling the global financial architecture "outdated dysfunctional, and unfair," Guterres said it needed deep, structural reform. "And the same can be said of the United Nations Security Council."