LONDON -- There will be roundtable meetings, one-on-one chats and a group photo against a picturesque backdrop. When leaders of some of the world's richest nations meet Friday at the English seaside for a three-day Group of Seven summit, much of the choreography will be familiar.

But the world has changed dramatically.

Since the G7 last met two years ago, the coronavirus pandemic has killed more than 3.7 million people and decimated economies with lockdowns and layoffs.

So when British Prime Minister Boris Johnson welcomes U.S. President Joe Biden and the leaders of France, Germany, Italy, Japan and Canada to the cliff-ringed Carbis Bay beach resort in southwest England, pandemic recovery -- "building back better," in a phrase both Biden and Johnson like -- will top the agenda.

Johnson said the meeting would help move on from "a miserable period of competition and squabbling" that marked the early response to the pandemic.

"This is the moment for the world's greatest and most technologically advanced democracies to shoulder their responsibilities and to vaccinate the world, because no one can be properly protected until everyone has been protected," he said in an article published Thursday, a day before the summit's official start.

Before the pandemic, Johnson planned this to be a climate-dominated summit. He had wanted to make it a major staging post to November's international COP26 meeting on climate change in Glasgow, eliciting ambitious targets for slashing carbon emissions and expanding green industries.

That's still on the agenda, but the meeting will be dominated by COVID-19, with discussions focusing on physical and economic recovery and building resilience against future pandemics. Lest anyone forget that the virus is still raging, there will be daily coronavirus tests for attending politicians, diplomats, staff and journalists.

Biden made a vaccine pledge before the meeting got underway, announcing that the U.S. will buy 500 million more doses of the Pfizer vaccine to share with poorer countries over the next year.

That upped the pressure on Johnson, who has not yet sent any of Britain's vaccine doses abroad. Almost four-fifths of adults in the U.K. have had the first of two shots.

Johnson said Thursday that Britain would donate "millions" of doses from surplus stocks -- though he didn't say when.

Johnson also noted that the British government helped fund development at Oxford University of the AstraZeneca vaccine, which accounts for one in three doses around the world.

France said President Emmanuel Macron wanted to see "results and not just announcements" on vaccines.

"We need a specific calendar -- how many people worldwide and especially in Africa will be vaccinated" before a meeting of the G20 in Rome in October, an official in the president's office said, noting that Africa has received under 2% of the world's coronavirus vaccine doses.

Even without the pandemic, this would be a moment of flux for the rich countries' club. It's a first G7 summit for Biden and Japan's Yoshihide Suga, who took office in September. Italy's Mario Draghi is a veteran of senior international roles but has been prime minister only since February. And it's the swan song for German Chancellor Angela Merkel, who will leave office in the coming months after 16 years in power.

The summit is seen as a major test for Johnson, a divisive leader at home and abroad whose two years in office have been dominated by the consecutive crises of Brexit and the pandemic.

Johnson's eve-of-summit meeting with Biden on Thursday will be a chance to underscore the trans-Atlantic alliance and to set out his vision of a post-Brexit "Global Britain" as a midsized country with an outsized role in international problem-solving.

That may be a challenge, given the distrust in European capitals and Washington surrounding the U.K.'s decision to leave the EU and the messy process of separation.

Biden has called the blustering Johnson a "clone" of former President Donald Trump and has expressed concern about the destabilizing effect of Brexit on Northern Ireland, the only part of the U.K. that borders the bloc.

He is likely to press Johnson to soothe tensions. Biden's national security adviser, Jake Sullivan, told reporters aboard Air Force One that the president's commitment to Northern Ireland's Good Friday peace accord was "rock solid."

Like many prime ministers before him, Johnson plans to summon the spirit of wartime leader Winston Churchill as he tries to charm the president. The two leaders are set to sign a new Atlantic Charter -- a 21st century version of the 1941 agreement between Churchill and President Franklin D. Roosevelt that helped lay the foundations for the United Nations and NATO. The British government says Biden and Johnson will pledge to work together for goals including more democracy, greater security and freer trade, and will set up a task force aimed at re-starting travel between the two nations, disrupted by pandemic restrictions.

Britain may be the host, but Renata Dwan, deputy director of the Chatham House international affairs think-tank, said it's striking how much the summit agenda is U.S.-driven.

A proposal for a minimum 15% tax on multinational companies, agreed by G7 finance minister last week, came from the U.S. Biden took allies by surprise when he announced a patent waiver on coronavirus vaccines last month -- a move no other G7 country has yet followed.

Biden will reassure allies at the G7 -- and NATO, when he attends a meeting of the military alliance in Brussels next week -- that the U.S. is back as a reliable ally after the Trump years.

But this is a nervous global moment, with Russia increasingly destabilizing its neighbors and Biden continuing Trump's strong stance against economic and political rival China. Many in Europe feel that American attention is increasingly focused eastward.

Dwan said the G7 summit is "a chance to say `multilateralism is back,"' but big differences lurk beneath the surface.

"You have no real fundamental agreement on whether the focus of the G7 is on the future -- build back better, which is what the U.K. wants to do -- or immediate issues: crisis response now in terms of vaccine supply, manufacturing, distribution," she said.

"Everyone's going to try to play really nice," she said. But "in terms of real deals, there's some real problems."

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Associated Press writer Angela Charlton in Paris contributed.