The US will buy 500 million more doses of the Pfizer coronavirus vaccine to share through the global Covax alliance for donation to 92 lower income countries and the African Union over the next year.
Joe Biden, the US president, was set to make the announcement Thursday in a speech before the start of the G7 summit.
Some 200 million doses – enough to fully protect 100 million people – would be shared this year, with the balance to be donated in the first half of 2022.
National security adviser Jake Sullivan said Mr Biden was committed to sharing vaccines because it was in the public health and strategic interests of the US.
Photographers wait for Mr Biden to arrive at Mildenhall
Credit: REUTERS/Andrew Boyers
Air Force One arrived at RAF Mildenhall on Wednesday
Credit: AP Photo/Matt Dunham
US president Joe Biden and first lady Jill Biden disembark Air Force One
Credit: REUTERS/Kevin Lamarque
Mr Biden said he would rally democracies in an ideological and economic struggle against China and face down provocations from Russia as he left Washington on his first overseas trip as president.
"Making clear to Putin and China that Europe and the United States are tight," Mr Biden said in when asked the goal of his busy trip to Britain, Belgium and Switzerland, where he will meet Vladimir Putin.
Mr Biden arrived in Cornwall on Wednesday evening and will hold bilateral talks with Boris Johnson on Thursday before the three-day G7 leaders’ summit opens on Friday.
G7 Summit agenda
He will head to Brussels for Nato and US-EU summits early next week before an all-important first meeting with Russian president Vladimir Putin in Geneva on June 16.
Mr Biden has made clear the primary goal of his first international trip as president is to signal that "America is back" on the world stage.
The US president is eager to rebuild ties with allies after four years of strained relations and the hollowing out of multinational institutions under his predecessor’s "America First" agenda.
He will also announce a global coronavirus vaccination strategy, and seek to firm up consensus on climate change goals.
But almost every policy sphere is overshadowed by what Mr Biden believes is a historic struggle between democracies led by the US and autocracies led by Beijing.
Writing in the Washington Post before he left the US, Mr Biden said: "This is a defining question of our time: Can democracies come together to deliver real results for our people in a rapidly changing world?
"I believe the answer is yes. And this week in Europe, we have the chance to prove it."
He said the G7 must focus on ensuring that market democracies and "not China or anyone else write the 21st-century rules around trade and technology."
President Joe Biden’s European tour itinerary
Part of the response Mr Biden is expected to push at the G7 is the idea of offering developing countries a “high standard alternative” to China for upgrading physical, digital and health infrastructure.
It would be the first explicit Western challenge to China’s "Belt and Road Initiative,” the massive infrastructure building program that has extended Beijing’s diplomatic and political clout throughout Africa, Asia, and Europe.
Mr Biden will find a sympathetic audience when he raises China at the G7.
Mr Johnson, who is hosting the summit, has made “common values” and strengthen the alliance of democracies, especially in the Indo-Pacific region, a major theme.
He has also invited four guest nations – South Korea, South Africa, Australia and India – in what some have described as an attempt to build an alliance to counterbalance China.
Scott Morrison, Australia’s prime minister, on Tuesday said he would use the Cornwall summit to seek backing from G7 nations to face down “economic coercion” from China.
Speaking in Perth before he flying to Cornwall, he also said growing competition between China and its neighbours in the Indo-Pacific need to be managed to avoid conflict.
But he will also have to address major differences with some allies on other policies.
He has already expressed frustration with Germany’s decision to forge ahead with the Nord Stream 2 gas pipeline with Russia.
Mr Biden believes the pipeline will undermine the security of Ukraine and other eastern European countries, but has stopped short of sanctioning it.
He will also issue a stern warning to both Boris Johnson and the European Union not to "imperil" the Northern Ireland peace process.
While Mr Biden was on Air Force One over the Atlantic his national security adviser Jake Sullivan said the president harbours "very deep" concerns on the issue.
Mr Sullivan said the president believes the post-Brexit Northern Ireland Protocol is "critical" to ensuring that the Good Friday Agreement is protected, as Britain and the EU try to resolve the issue of checks in the Irish Sea.
He said both sides must continue with negotiations, adding: "But whatever way they find to proceed must, at its core, fundamentally protect the gains of the Good Friday Agreement and not imperil that.
"And that is the message that President Biden will send when he is in Cornwall."
Mr Biden is proud of his Irish heritage and, according to aides, follows events in Northern Ireland very closely.