Joe Biden makes his presidential debut at the G7 on Friday as America's partners re-focus their collective heft on pandemic recovery and climate change after the psychodramas of the Trump era.

British Prime Minister Boris Johnson, this year's chair of the club of wealthy nations, will convene the virtual talks at 1400 GMT, vowing to free up any surplus coronavirus vaccines for poorer countries at a future date.

White House officials said Biden would pledge $4 billion (4.6 billion euros) in US aid to the UN's Covax programme to buy vaccines for global distribution. The European Union plans to double its own Covax funding to one billion euros, an EU source said.

But French President Emmanuel Macron demanded richer nations go further by transferring 3-5 percent of their existing stock to Africa.

"It's an unprecedented acceleration of global inequality and it's politically unsustainable too because it's paving the way for a war of influence over vaccines," he told the Financial Times, as Russia and China step up free or low-cost distribution of their own jabs.

British junior foreign minister James Cleverly said the government's "first duty is to protect our own people".

"But we are also a global force for good and that's why we are leading the world in calls to ensure that the poorest countries in the world are also made safe," he told BBC radio.

"And we are not going to use vaccine distribution as some kind of -- as some countries are doing -- some short-term diplomatic leverage."

Absent China looms large

Following the summit, Biden, Johnson and EU leaders in the G7 will join another gathering online, the annual Munich Security Conference, to discuss "renewing transatlantic cooperation".

Biden will become the first US president to address the Munich meeting, underlining a decisive shift after cooperation was all but broken under his go-it-alone predecessor Donald Trump.

Since taking office last month, the Democrat has re-committed the United States to action on global warming and to the World Health Organization (WHO). Friday marked its formal re-entry to the Paris climate accord.

Biden's participation in both the G7 and Munich meetings heralds "a broad-ranging, confident, clarion call to have the transatlantic alliance and partnership stand up together", a senior Biden administration official told reporters.

However, Biden has maintained one Trumpian perspective -- mistrust of China.

Beijing is not part of the G7 -- which comprises Britain, Canada, France, Germany, Italy, Japan and the US -- and Washington is repositioning rich democracies as a counterweight to China amid mistrust of its initial handling of Covid-19.

Meanwhile, Britain wants the G7 to back a proposed pandemic treaty to enhance early warning and data transparency in case of future outbreaks.

London denies it has China in its sights, but the Asian power has been widely accused of covering up the emergence of the virus in late 2019 and depriving the WHO of vital early information.

'Never again'

Johnson will also use the G7 to push for the WHO and international scientists to work on development of new vaccines in just 100 days. That would represent a dramatic decrease on the 300-odd days that were needed to come up with jabs against the coronavirus -- in itself a breakneck achievement.

"The development of viable coronavirus vaccines offers the tantalising prospect of a return to normality, but we must not rest on our laurels. As leaders of the G7 we must say today 'never again'," the prime minister said.

Now that inoculation campaigns are picking up speed, in the West at least, G7 leaders also hope to look past the pandemic to financial recovery after lockdowns ravaged many economies.

"President Biden will also discuss (the) need to make investments to strengthen our collective competitiveness and the importance of updating global rules to tackle economic challenges such as those posed by China," the White House said.

Biden will in addition promote "a robust agenda of measures to address the global climate crisis", as Britain prepares to host the UN's next climate summit, COP26, in the Scottish city of Glasgow in November.

COP26 will cap a busy diplomatic year that will flesh out Johnson's vision of a "Global Britain" following its Brexit withdrawal from the EU. He hopes to host the G7's leaders in person in June, at a resort in southwest England.