SHARM EL-SHEIKH, Egypt (AP) — “Cooperate or perish,” the United Nations chief told dozens of leaders gathered Monday for international climate talks, warning them that the world is “on a highway to climate hell” and urging the two biggest polluting countries, China and the United States, to work together to avert it.

This year’s annual U.N. climate conference, known as COP27, comes as leaders and experts have raised increasing alarm that time is running out to avert catastrophic rises in temperature. But the fire and brimstone warnings may not quite have the effect as they have had in past meetings because of multiple other challenges of the moment pulling leaders’ attention — from midterm elections in the US to the Russia-Ukraine war.

More than 100 world leaders will speak over the next few days at the gathering in Egypt. Much of the focus will be on national leaders telling their stories of being devastated by climate disasters, culminating Tuesday with a speech by Pakistan Prime Minister Muhammad Sharif, whose country’s summer floods caused at least $40 billion in damage and displaced millions of people.

“Is it not high time to put an end to all this suffering,” the summit’s host, Egyptian President Abdel Fattah el-Sissi, told his fellow leaders. “Climate change will never stop without our intervention… Our time here is limited and we must use every second that we have.’’

El-Sisi, who called for an end to the Russia-Ukraine war, was gentle compared to a fiery United Nations Secretary-General Antonio Guterres, who said the world “is on a highway to climate hell with our foot on the accelerator.”

He called for a new pact between rich and poor countries to make deeper cuts in emissions with financial help and phasing out of coal in rich nations by 2030 and elsewhere by 2040. He called on the United States and China — the two biggest economies — to especially work together on climate, something they used to do until the last few years.

“Humanity has a choice: cooperate or perish,” Guterres said. “It is either a Climate Solidarity Pact – or a Collective Suicide Pact.”

Guterres insisted, “Today’s urgent crises cannot be an excuse for backsliding or greenwashing.”

But bad timing and world events were hanging over the gathering.

Most of the leaders are meeting Monday and Tuesday, just as the United States has a potentially policy-shifting midterm election. Then the leaders of the world’s 20 wealthiest nations will have their powerful-only club confab in Bali in Indonesia days later.

Leaders of China and India — both among the biggest emitters — appear to be skipping the climate talks, although underlings are here negotiating. The leader of the top polluting country, US President Joe Biden, is coming days later than most of the other presidents and prime ministers on his way to Bali.

“There are big climate summits and little climate summits and this was never expected to be a big one,” said Climate Advisers CEO Nigel Purvis, a former US negotiator.