For President Trump, the meetings marked another closing lap on the world stage before handing power to the Biden administration in January.
He will also use Sunday's session to call on those leaders yet to make net-zero commitments to make the same pledge, just under a month before Britain co-hosts the Climate Ambition Summit on December 12.
G20 nations have contributed more than $21 billion to combat the pandemic, which has infected 56 million people globally and left 1.3 million dead, and injected $11 trillion to "safeguard" the virus-battered world economy, organisers said.
The case has sparked an worldwide outcry and tarnished the global reputation of Crown Prince Mohammed bin Salman (MBS).
Trump, who continues to reject his election loss, took part Friday in an Asia-Pacific summit.
Ahead of the summit, European Commission President Ursula von der Leyen said she hoped the USA would adopt a more multilateralist stance under Biden.
She also expressed hope that America's "new President-elect" Joe Biden will "increase multilateral cooperation" in areas like health and climate change, noting that until now "the United States has resisted engaging" in a rebuke of Trump's isolationist policies. Members are expected to finalize a framework for providing poor nations debt-relief, alongside continuing discussions for financing covid-19 vaccine collaborations.
On Friday, Turkish President Recep Tayyip Erdogan and King Salman of Saudi Arabia spoke by telephone, according to statements from both leaders.
In a bid to liven up the event, which takes place in a gloomy global atmosphere, Saudi Arabia's King Salman hosted an evening musical gala on the eve of the event and projected a group photo of the world leaders onto the ruins of the historical town of Diriyah, close to the capital Riyadh.
"President Erdogan and King Salman agreed to keep channels of dialogue open to improve bilateral ties and overcome issues", the Turkish presidency said in a statement, adding the two men had also discussed the G-20 summit. Erdogan was scheduled to speak at the summit on Saturday.