UNITED NATIONS — Secretary-General Antonio Guterres warned the U.N.’s first-ever virtual meeting of global leaders Tuesday that the world is facing an “epochal” health crisis, the biggest economic calamity and job losses since the Great Depression, threats to human rights — and the risk of a new Cold War between the U.S. and China.

In his bleak state of the world speech to the U.N. General Assembly’s annual high-level meeting, the U.N. chief said that the coronavirus that “brought the world to its knees” was but “a dress rehearsal for the world of challenges to come.”

He called for global unity, first and foremost to fight the pandemic, and sharply criticized populism and nationalism for failing to contain the virus, and for often making things worse.

Days after the pandemic shut down big parts of the world in March, Guterres called for a global cease-fire to tackle it. On Tuesday, he appealed for a 100-day push by the international community, led by the Security Council, “to make this a reality by the end of the year.”

“At the same time, we must do everything to avoid a new Cold War,” Guterres added.

Reiterating a warning he made to world leaders a year ago about increasing U,S.-China rivalry, Guterres said, “We are moving in a very dangerous direction.”

“Our world cannot afford a future where the two largest economies split the globe in a Great Fracture — each with its own trade and financial rules and internet and artificial intelligence capacities,” Guterres said. “A technological and economic divide risks inevitably turning into a geo-strategic and military divide. We must avoid this at all costs.”

In his appeal for a global cease-fire, Guterres said ending wars in the Middle East and Africa is critical to defeating the coronavirus.

“There is only one winner of conflict during a pandemic: the virus itself,” he said.

Guterres said armed movements from Cameroon to Colombia, the Philippines and beyond responded to his original appeal even if several cease-fires they announced didn’t last. But there are reasons to be hopeful, he said, pointing to a new peace agreement in Sudan, the launch of Afghan peace negotiations, and cease-fires largely holding in Syria’s Idlib province, Ukraine and elsewhere.

The U.N. chief delivered his speech in the vast General Assembly Hall, where only one mask-wearing diplomat from each of the U.N.’s 193 member nations was allowed, spread out in the chamber.

“In a world turned upside down, this General Assembly Hall is among the strangest sights of all,” Guterres said. “The COVID-19 pandemic has changed our annual meeting beyond recognition. But it has made it more important than ever.”

Brazil’s President Jair Bolsonaro, whose country by tradition is the first speaker, trumpeted his focus on the economy in dealing with the pandemic, lambasting “segments of the Brazilian media” for “spreading panic” by encouraging stay-at-home orders and prioritizing public health over the economy.

“They almost brought about social chaos to the country. But our administration, in a bold step, put in place several economic measures that prevented a greater evil,” he said, pointing to various relief programs.

Brazil has reported the second-highest coronavirus death toll after the United States, with over 136,000 dead, according to statistics collected by Johns Hopkins University.

Turkish President Recep Tayyip Erdogan criticized the start of the pandemic “where countries were left on their own,” stressing that “effective multilateralism requires effective multilateral institutions.” He urged rapid implementation of “comprehensive and meaningful reforms, starting with the restructuring of the Security Council,” the U.N.’s most powerful body with five veto-wielding members — the U.S., China, Russia, Britain and France.