The two-day leaders' summit, which opened on Saturday, will address pressing global issues, including the battle against the coronavirus, how to restart damaged economies and potential financial aid for poor countries hit hard by the pandemic.
Also on the agenda and discussed in complementary events are women's empowerment and sustainable energy development.
King Salman of Saudi Arabia opened the summit on Saturday with a video address calling on rich countries to ensure that poor nations also received the tools to fight Covid-19, the disease caused by the coronavirus.
"We must work to create the conditions for affordable and equitable access to these tools for all peoples," the 84-year-old monarch said. "At the same time, we must prepare better for any future pandemic."
Also on the agenda is potential debt relief to help poor countries deal with the economic fallout of the pandemic, and a European Union proposal for an international treaty on pandemics.
"An international treaty would help us respond more quickly and in a more coordinated manner," Charles Michel, the president of the European Council, is expected to tell the leaders on Sunday.
President Trump is slated to participate, according to senior administration officials, although the agenda could underline the United States' failure to control the spread of the virus and Mr. Trump's preference for traditional energy sources like oil and coal.
The G-20 is a forum for the 19 nations with the world's largest economies and the European Union to discuss global economic affairs. The organization's presidency rotates among five groups of countries, with one country in each group holding the position at a time. Saudi Arabia, in a group with Canada, Australia and the United States, was named president for the first time last December. It is the first Arab country to host the summit.
The kingdom celebrated the title as a recognition of the importance of the world's largest oil exporter in the global economy as well as an opportunity to showcase vast social and economic reforms being championed by Prince Mohammed, whose father, King Salman, became the Saudi monarch in 2015.
Since then, Prince Mohammed has lifted some restrictions on women, promoted entertainment and tourism, and advanced plans to diversify the economy away from oil. He has also led the Saudi military into Yemen's civil war, which has become a grave humanitarian crisis, and locked up clerics, women's rights activists and even members of the royal family.