(Bloomberg) -- President Donald Trump and Chinese President Xi Jinping clashed during a virtual United Nations General Assembly, underscoring the widening rift between the two biggest economies that the UN’s chief said risks breaking up the world into rival spheres of influence.

Trump, who in recent years has used the UN stage to single out smaller U.S. rivals such as North Korea and Iran, centered his UN speech mostly on China, accusing Beijing of polluting the oceans and air while lying to the world about Covid-19. Without naming Trump, Xi slammed leaders who politicize the virus and seek to avoid globalization by “burying their heads in the sand like an ostrich.”

“We are moving in a very dangerous direction,” Secretary-General Antonio Guterres warned in his opening speech. “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.”

The U.S.-China feud framed the opening debate at the annual UN General Assembly. Normally the gathering brings about 10,000 diplomats to Manhattan, but it’s being held virtually this week, another victim of the Covid-19 pandemic.

World leaders were asked to submit videos up to 15 minutes long to play in the General Assembly chamber, but that restriction was quickly breached by the much wordier speeches by several heads of state. Other major issues and themes on Tuesday include:

Covid-19 Pandemic

The coronavirus pandemic loomed over all the proceedings, mentioned by every speaker. Secretary-General Guterres made the illness the focus of his remarks, saying it had wiped away a decade of progress in developing nations and urging more aid for poorer countries struggling with the outbreak.

“We face simultaneously an epochal health crisis, the biggest economic calamity and job losses since the Great Depression and dangerous new threats to human rights,” Guterres said. “Covid-19 has laid bare the world’s fragilities.”

Lack of Female Leaders

After years of focus on gender diversity issues, the line-up of speakers on the opening day at the UN highlighted how few female heads of state there are. The 35 speakers scheduled on Tuesday are all men. It’s not until late on the assembly’s second day that the first female leader is scheduled to take the virtual podium: Zuzana Caputova, the president of Slovakia. She’ll be followed on Wednesday by Bolivia’s Jeanine Anez.

China’s Climate Pledge

Minutes after Trump criticized China’s environmental record, Xi made news with a commitment to become carbon neutral by 2060, a faster target than Beijing was previously willing to set. He also reiterated his goal for emissions to peak before 2030.

“Humankind can no longer afford to ignore the repeated warnings of nature and go down the beaten path of extracting resources without investing in conservation, pursuing development at the expense of protection, and exploiting resources without restoration,” Xi said.

Iran Nuclear Deal

There was little talk in the opening speeches of the biggest issue dividing the UN Security Council: America’s insistence that international sanctions on Tehran “snap back” amid U.S. claims that the 2015 Iran nuclear deal is essentially dead.

The U.S. position isn’t supported by allies or rivals on the Security Council, and even Guterres has signaled the questionable legality of the U.S. demand.

Trump was surprisingly brief in his comments about the crisis, simply saying that the U.S. “withdrew from the terrible Iran Nuclear Deal and imposed crippling sanctions on the world’s leading state sponsor of terror.”

One leader who wasn’t quiet on the topic was Iran’s President Hassan Rouhani, who denounced the U.S. as the world’s nuclear-armed danger. “They accuse us without any foundation of trying to build nuclear weapons,” Rouhani said in his remarks.

He said it was “time to say no to the era of bullying and arrogance.”

Putin’s Vaccine Offer

Russia’s president typically skips the UNGA, but this year he made an offer to UN staff struggling to manage covid-related crises: free access to a controversial vaccine Russia has counters the coronavirus.

“We offer our vaccine for free for voluntary inoculation of UN workers,” Putin said, even though Russia’s quick deployment of the medicine and the lack of rigorous testing has limited its appeal.

The Russian leader also called for an international online conference to discuss progress in fighting the pandemic, an offer that may be more amenable to other leaders.

Virtual Hiccups

Even with world leaders filing a week’s worth of video speeches for the general assembly, that doesn’t mean the UN headquarters is empty. Hallway diplomacy may be limited, but masked ambassadors sat several seats apart in a quiet UN auditorium as they listened to the leaders speaking.

Brazilian President Jair Bolsonaro’s speech was interrupted just a few minutes after it started, with the screen going black before the video was restarted. After that, the technical difficulties seemed to be brought under control.

©2020 Bloomberg L.P.