UN Secretary-General Antonio Guterres on Monday urged concrete action at the Climate Action Summit that he convened amid a worsening climate crisis.

Speaking at the opening ceremony of the summit, Guterres said, "This is not a climate talk summit. We have had enough talk. This is not a climate negotiation summit because we don't negotiate with nature."

"From the beginning, I said the ticket to entry is not a beautiful speech, but concrete action," he added.

Guterres cited climate disasters from rising seas to acidifying oceans, from melting glaciers to bleaching corals, from spreading droughts to burning wildfires, from scorching heatwaves to intense storms.

In tackling the climate change, he said, "Technology is on our side. Readily-available technological substitutions already exist for more than 70 percent of today's emissions."

He called for stopping "subsidizing a dying fossil fuel industry and building more and more coal power plants."

He also urged accelerating financial support for climate efforts, including the replenishment of the Green Climate Fund, fulfilling the commitment by developed countries to mobilize 100 billion U.S. dollars a year from public and private sources by 2020 for mitigation and adaptation in developing countries.

Stressing the importance of adaptation, he said even if the world succeeds in reducing emissions, many people are already living with the dramatic effects of climate change. Adaptation has therefore become a top priority and an essential condition for increasing the resilience of countries and communities and avoiding human suffering.

The opening ceremony also included a session of dialogue between Guterres and youth representatives.

Some 100 government, business and civil society leaders, many of them heads of state and government, are expected to speak at the summit.

The meeting serves as a platform for climate leaders to raise political ambition that will result in enhanced and irreversible commitments to action in national climate plans to significantly cut emissions.

Guterres has prioritized nine action portfolios: finance, energy transition, industry transition, nature-based solutions, infrastructure, cities and local action, resilience and adaptation, youth and mobilization, the social transition, and mitigation ambition.

The commitments and actions made at the summit will be put in a summary by the UN secretary-general at the end of the meeting.