China's President Xi Jinping and U.S. President Donald Trump delivered contrasting virtual speeches to the United Nations General Assembly this week during celebrations of the organization's 75th anniversary.

Xi championed China's version of internationalism and encouraged common respect and cooperation among countries. Trump hailed the America First policy and said China was the source of COVID-19 and other world problems.

The UN began its anniversary celebrations Monday. It traces its foundation back to the signing of its Charter by 51 founding members June 26, 1945, in San Francisco, California.

UN Secretary-General Antonio Guterres opened the session Monday by appealing for a revival of multilateralism - the organization's cornerstone. He appealed for a "new multilateralism" and encouraged countries to "work together to improve world governance."

Xi positioned himself as a champion of a rules-based international order. He dismissed the law of the "strong fist" - possibly a reference to the bullying China has often accused Trump for. "Relations among countries and coordination of their interests must be based on rules and institutions only. They must not be lorded over by those who wave a strong fist," Xi said.

Xi criticized Cold War mentalities, ideological lines and zero-sum games. These, Xi said, "are no solution to a country's own problem (and) still less an answer to mankind's common challenges."

"Unilateralism is a dead end," Xi said.

Xi said China was the largest developing country in the world but was committed to peaceful, open, cooperative and common development.

"We will never seek hegemony, expansion or sphere of influence," Xi said. "We have no intention to fight either a Cold War or a hot war with any country. We will continue to narrow differences and resolve disputes with others through dialogue and negotiation. We do not seek to develop ourselves only or engage in a zero-sum game."

He promised China would remain open to the world while pursuing its version of internationalism - or a "new development paradigm" that would benefit the world.

"We will not pursue development behind closed doors," Xi said. "Rather, we aim to foster, over time, a new development paradigm with domestic circulation as the mainstay and domestic and international circulations reinforcing each other. This will create more space for China's economic development and add impetus to global economic recovery and growth."

Trump condemned China - most especially for COVID-19. "The United Nations must hold China accountable for its actions," Trump said. He called COVID-19 "The China Virus."

Trump has blamed China for mishandling the pandemic although he has been criticized at home for his own management of the pandemic. The U.S. this week reported it had 200,000 COVID-19-related deaths and 7.1 million cases - the worst in the world.

Trump demanded the international community join him in investigating China's actions - which he said were the direct cause of the suffering.

"For decades, the same tired voices proposed the same failed solutions, pursuing global ambitions at the expense of their own people. But only when you take care of your own citizens will you find a true basis for cooperation. As president, I have rejected the failed approaches of the past and I am proudly putting America first - just as you should be putting your country's first," he said. "That's OK. That's what you should be doing."