United Nations Secretary General Antonio Guterres told countries gathered at the start of the COP27 summit in Egypt on Monday they face a stark choice: work together now to cut emissions or condemn future generations to climate catastrophe.

The speech set an urgent tone as governments sit down for two weeks of talks on how to avert the worst of climate change, even as they are distracted by Russia’s war in Ukraine, rampant consumer inflation and energy shortages.

"Humanity has a choice: cooperate or perish,” Guterres told delegates gathered in the seaside resort town of Sharm el-Sheikh.

He called for a pact between the world's richest and poorest countries to accelerate the transition from fossil fuels and funding to ensure poorer countries can reduce emissions and cope with the climate impacts that have already occurred.

"The two largest economies – the United States and China – have a particular responsibility to join efforts to make this pact a reality," he said.

Despite decades of climate talks - the Egypt COP is the 27th Conference of the Parties - progress has been insufficient to save the planet from excessive warming as countries are too slow or reluctant to act, he noted.

"Greenhouse gas emissions keep growing. Global temperatures keep rising. And our planet is fast approaching tipping points that will make climate chaos irreversible," he said. "We are on a highway to climate hell with our foot on the accelerator."

Former U.S. Vice President Al Gore, also speaking at the event, said global leaders have a credibility problem when it comes to climate change. He criticized developed nations' ongoing pursuit of gas resources in Africa, which he described as "fossil fuel colonialism."

"We have a credibility problem all of us: We're talking and we're starting to act, but we're not doing enough," Gore said.

"We must see the so-called 'dash for gas' for what it really is: a dash down a bridge to nowhere, leaving the countries of the world facing climate chaos and billions in stranded assets, especially here in Africa," he said.