Buhari made the call on Friday while addressing world leaders at the 76th Session of UN General Assembly (UNGA) in New York.
G20 members are Argentina, Australia, Brazil, Canada, China, the European Union, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia.
Others include Saudi Arabia, South Africa, South Korea, Turkey, the United Kingdom, and the United States. Spain is a permanent guest invitee.
Buhari requested outright debt cancellation for countries facing the most severe challenges occasioned by COVID-19.
The Nigerian leader recalled developing countries faced unsustainable debt burdens even before coronavirus outbreak.
Buhari observed the pandemic had increased the risk of deepening debt, where public resources are allocated to servicing and repayments at the expense of financing for critical needs.
The President commended the drive of international financial institutions and the G20 aimed at mitigating the economic situation of indebted nations.
“The is an urgent need to consider expansion and extension of the Debt Service Suspension Initiative to include all Developing, Least Developed Countries and Small Island Developing States facing fiscal and liquidity challenges”, he said.
The Buhari administration is being criticized for demanding that the Nigerian Senate approve fresh $4.054bn and €710million credit.
In its condemnation, the People’s Democratic Party (PDP) accused the All Progressives Congress (APC) government of trying to sell the country.
The opposition warned that approval of the latest request, plus an additional N5.62trillion loan proposed for the 2022 budget will jerk Nigeria’s liability up to N40trillion.
The presidency has provided a breakdown and insists the borrowings are needed to fund projects and development programmes.