"We can not let the COVID pandemic lead to a debt pandemic", Guterres told reporters.
"We will now speak with (global vaccine alliance group) GAVI about when these negotiations will begin because I am somewhat anxious that nothing has been done on that yet", she said.
"We are aware of the scope of our responsibility but also of the difficulty of our task", he said, adding: "The health and socio-economic answer to the pandemic, which has caused and continues to cause enormous suffering tomankind and has already struck significant blows to the global economy, will obviously continue to be at the top of our agenda, to keep high the commitment of the worldwide community in the reaction to COVID-19".
While G20 countries have contributed billions of dollars toward developing a vaccine for the virus, they have also mostly focused on securing their own vaccine supplies.
The Chinese president also called for joint efforts from G-20 to tackle climate and other environmental challenges, and protect the blue planet.
Three G20 leaders participating in the summit have been infected by the coronavirus this year: British Prime Minister Boris Johnson, Brazilian President Jair Bolsonaro and Trump.
However, the final document lacked detail on how that would be funded.
In a comment echoed by other world leaders, French President Emmanuel Macron said Saturday the coronavirus crisis was "a test for the G20", stressing there "will be no effective response to the pandemic unless it is a global response".
This spirit is necessary today more than ever to face the impacts of this pandemic and to build a prosperous future for the people of the world.
The communique did not offer a firm commitment.
In excerpts of a draft G20 communique on Friday, leaders note that the coronavirus crisis had hit the most vulnerable in society the hardest, and said some countries may need debt relief beyond a temporary freeze in official debt payments that ends in June 2021.
G20 finance ministers will examine the recommendation when the International Monetary Fund and World Bank meet next spring "if the economic and financial situation requires" an extension by another six months, it said.
They are also scheduled to discuss the development of agreements made at the previous summit, including debt suspension support for low-income countries and strengthening the multilateral trading system.
Ahead of the summit, European Commission President Ursula von der Leyen said she hoped the U.S. will adopt a more multilateralist stance under the incoming administration of Joe Biden. The World Health Organization says more cases of COVID-19 have been reported in the past four weeks than in the first six months of the pandemic.
Von der Leyen also added that she expected consensus and a "new momentum from the new United States administration" on climate change and a reversal of Trump's withdrawal from the Paris climate accord.
This was the first time that Saudi Arabia had the honor of holding the Presidency of the G20, and it turned out to be a very challenging year.
"The Paris accord was not created to save the environment".
China has put in place the world's biggest clean energy system, and has led the world in the output and sales of new energy vehicles for five years running.
But human rights activists hope that, without reform, the kingdom is never granted hosting rights again.
I now adjourn the Riyadh G20 Summit.