CARBIS BAY, ENGLAND -- Group of Seven leaders brought pledges to share vaccine doses and make a fairer global economy Friday to a seaside summit in England, where British Prime Minister Boris Johnson said the coronavirus pandemic should not be allowed to leave a "lasting scar" on the world.

The wealthy nations' leaders were all smiles and unity as Johnson greeted them on the freshly raked sand of Carbis Bay, but they jostled over who was doing most to help the world's poorer nations fight COVID-19.

Recovery from the pandemic was set to dominate their discussions, and members of the wealthy democracies club committed to sharing at least 1 billion vaccine shots with struggling countries. That includes a pledge from U.S. President Joe Biden to share 500 million doses, and a promise from Johnson for another 100 million shots.

Host Britain said the G7 will also announce a package of measures aimed at reducing the chances of another pandemic. The U.K. government said the grandly titled "Carbis Bay Declaration" will aim for a 100-day goal to develop vaccines, treatments and diagnostics for future disease and to bolster surveillance for new illnesses.

The group will also pledge to strengthen the World Health Organization, which former President Donald Trump pulled out of and Biden rejoined.

Johnson said the goal of the measures was "to make sure that never again will we be caught unawares."

Opening three days of talks in Cornwall, southwest England, Johnson warned that world leaders must not repeat errors made over the past 18 months -- or those made in the recovery from the 2008 global financial crisis.

"It is vital that we don't repeat the mistake of the last great crisis, the last great economic recession in 2008, when the recovery was not uniform across all parts of society," he said after leaders posed for a formal "family photo" by the sea.

"And I think what's gone wrong with this pandemic, and what risks being a lasting scar, is that I think the inequalities may be entrenched," Johnson added.

The leaders of the G7 -- which also includes the United States Canada, France, Germany, Italy and Japan -- hope the meeting at the resort will also energize the global economy. Beneath moody dark skies, the group walked away from the photo as cheerful as children who had just built a sand castle.

As Johnson led the politicians off the beach, French President Emmanuel Macron threw his arm around the shoulders of Biden, whom he was meeting for the first time. The White House later said the two men discussed COVID-19 and counterterrorism efforts in the Sahel region of Africa and would have a meeting on Saturday.

Facing criticism that they are hogging vaccines, the leaders are competing to be the global champion of so many wounded by the virus. With 3.7 million people lost in the pandemic, the world's richest democracies are eager to show themselves the champions of the afflicted.

German Chancellor Angela Merkel said she hoped the summit would show the world "we're not just thinking of ourselves." Macron sought to underscore that, noting that France had already shipped vaccine doses to the world's poor -- and gently chiding countries that have not by urging in a tweet for "clear goals" and "concrete commitments."

For Johnson, the first G7 summit in two years -- last year's was scuttled by the pandemic -- is a chance to set out his vision of a post-Brexit "global Britain" as a mid-sized country with an outsized role in international problem-solving.

On Friday Queen Elizabeth II -- Britain's biggest global star -- travelled from Windsor Castle near London for a reception with the leaders and their spouses at the Eden Project, a futuristic botanical garden housed inside domes that features the world's largest indoor rainforest.

The 95-year-old monarch drew laughter from her guests as she chided them during a group photo session: "Are you supposed to be looking as if you're enjoying yourself?"

Senior royals -- including heir to the throne Prince Charles, his son Prince William and William's wife, Kate -- joined the leaders for the reception and a dinner of roasted turbot, Cornish new potatoes and greens with wild garlic pesto cooked by a local chef.

The choice of an ecologically themed venue was deliberate. Climate change is also a top issue on the agenda, and hundreds of protesters gathered in Cornwall to urge the leaders to act, some dressed as sea creatures such as jellyfish. Demonstrators deployed a barge off the coast with two large inflatable figures depicting Biden and Johnson on board.

The G7 is also set to formally embrace a global minimum tax of at least 15% on multinational corporations, following an agreement reached a week ago by their finance ministers. The minimum is meant to stop companies from using tax havens to shift profits and to avoid taxes.

It represents a potential win for the Biden administration, which has proposed a global minimum tax as a way to pay for infrastructure projects, and it dovetails with the president's hope to focus the summit on ways the democracies can collaborate to build a more inclusive and fair global economy to help compete with rising autocracies like China.

But the main issue of the day was vaccines and the mounting pressure to outline global vaccine-sharing plans, especially as inequities in supply around the world have become more pronounced. In the U.S., there is a large vaccine stockpile, and the demand for shots has dropped precipitously in recent weeks.

Biden said the U.S. will donate 500 million Pfizer vaccine doses in the next year, 200 million of them by the end of 2021. That commitment was on top of 80 million doses Biden has already pledged to donate by the end of June. A price tag for the doses was not released, but the U.S. is now set to be the larges donor to the international COVAX vaccine effort, as well as its biggest funder.

Johnson said the first 5 million U.K. doses would be shared in the coming weeks, with the remainder coming over the next year. Macron said France would share at least 30 million doses globally by year's end. Germany plans to donate the same amount. White House officials said the G7 leaders on Friday committed to 1 billion doses in all.

The COVAX vaccination campaign got off to a slow start as richer nations locked up billions of doses through contracts directly with drug manufacturers. The alliance has distributed just 81 million doses globally, and large parts of the world, particularly in Africa, remain vaccine deserts.

Humanitarian workers welcomed the new donations but said the world needs more doses and sooner.

"We are still far from getting there," said United Nations Secretary General Antonio Guterres, who is due to attend the summit Saturday as a guest.

"We need a concerted effort. We need a global vaccination plan," he added. "If not the risk is there will still be large areas of the developing world where the virus spreads like wildfire."

Biden will wrap up his eight-day journey by meeting with Russian President Vladimir Putin in Geneva. Asked on the beach Friday what his message would be, Biden said, "I'll tell you after I deliver it."

Putin, in an interview with NBC, said Russia's relations with the U.S. had deteriorated to their lowest point in recent years.

Asked if he agreed with Biden's assessment in March that he is a killer, Putin laughed and said the criticism was part of America's macho attitude. "I've gotten used to attacks from all kinds of angles and from all kinds of areas under all kinds of pretext, and reasons of different caliber and fierceness and none of it surprises me," he said, adding, "So, as far as harsh rhetoric, I think that this is an expression of overall U.S. culture."

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Kirka reported from Falmouth, England. Associated Press writers Sylvia Hui in Falmouth and Jonathan Lemire in Plymouth, England, also contributed to this report.