Riyadh - Saudi Arabia hosts the G20 Summit Saturday in a first for an Arab nation, with the virtual forum dominated by efforts to tackle the coronavirus pandemic and the worst global recession in decades.

The two-day meeting of the world's wealthiest nations comes as President Donald Trump refuses to concede a bitter election and campaigners criticise what they call the G20's inadequate response to the crippling economic crisis.

World leaders will huddle virtually as international efforts intensify for a large-scale roll out of coronavirus vaccines after a breakthrough in trials, and as calls grow for G20 nations to plug a $4.5 billion funding shortfall.

Amid a raging pandemic, the summit -- usually an opportunity for one-on-one engagements between world leaders -- is reduced to brief online sessions of what some observers call "digital diplomacy".

The pandemic dampened Saudi Arabia's hopes of using the event as a grand coming-out party on the world stage. Still, the kingdom hosted a gala musical event on the eve of the summit and planned an aerial display of its passenger and aerobatic planes over Riyadh on Saturday.

German Chancellor,  Chinese and Russian presidents are among leaders expected to make speeches

Without an opportunity to take the traditional "family photo", at the gala they projected a group portrait of G20 leaders onto the ruins of the historical town of Diriyah, close to the capital.

Saudi Arabia's King Salman will preside over the meeting, with sources close to the organisers saying climate change was among the issues topping the agenda. German Chancellor Angela Merkel,  Chinese President Xi Jinping and Russian leader Vladimir Putin are among leaders expected to make speeches, the sources said. 

Trump will also participate, a US official said. Turkish President Recep Tayyip Erdogan will hold a briefing on Saturday, according to organisers."The G20 committed in March to do 'whatever it takes to overcome the pandemic and protect lives and livelihoods,'" British Prime Minister Boris Johnson said, referring to an earlier forum.

"As we meet this weekend, we must hold ourselves to account for that promise."

'Bolder measures' 

G20 nations have contributed more than US $ 21 billion to combat the pandemic, which has infected 56 million people globally and left 1.3 million dead, and injected US $ 11 trillion to "safeguard" the virus-battered world economy, organisers said.