UNITED NATIONS, Sept. 10 (Xinhua) -- UN Secretary-General Antonio Guterres said on Monday that climate change is a direct threat to mankind and youth should fight for their future and for global leadership to lead the campaign.

"Climate change is the defining issue of our time, and we are at a defining moment," he said. "We face a direct existential threat. Climate change is moving faster than we are."

"If we do not change course by 2020, we risk missing the point where we can avoid runaway climate change, with disastrous consequences for people and all the natural systems that sustain us," Guterres said in a major speech here at UN Headquarters, underlining the threat to future generations.

"That is why, today, I am appealing for leadership -- from politicians and leaders, from business and scientists, and from the public everywhere," he said. "We must break the paralysis. We have the moral and financial reasons to act. We have the tools to make our actions effective."

Guterres called on civil society and young people in particular to campaign for climate action. "Let us use the next year for transformational decisions in boardrooms, executive suites and parliaments across the world. Let us raise our sights, build coalitions and make our leaders listen."

The UN chief promised to make the same plea at the VIP-rich UN General Assembly General Debate beginning Sept. 25.

He already has scheduled a climate change summit for September 2019.