US President Joe Biden’s administration will provide 500 million doses of the Pfizer Covid-19 vaccine to about 100 countries over the next two years, US media report.
About 200 million doses will be distributed this year with the remainder distributed in 2022.
The US has been under pressure to do more to increase vaccination in poor countries.
The move comes as Mr Biden embarks on his first foreign trip as US president.
The White House is yet to officially comment on the plan to roll out 500 million doses worldwide.
But when asked if the US government had a vaccination strategy for the world, Mr Biden said: “I have one, and I’ll be announcing it,” before boarding Air Force One.
Mr Biden is set to meet European partners and Russian President Vladimir Putin.
The eight-day trip will begin with a meeting on Thursday with British Prime Minister Boris Johnson, before the two leaders set off for the G7 summit.
He will also meet the Queen at Windsor Castle and join his first Nato summit as president. He has said the trip is about “America rallying the world’s democracies”.
Meanwhile, a charter plane for the White House’s travelling press pool failed to take off from Washington after cicadas swarmed the plane’s engine. Reporters were stranded overnight at Dulles International Airport and a new plane was flown in as a replacement.
What can we expect from the G7 summit?
One of the major focuses of Mr Biden’s visit will be the G7 summit.
Their summit this year is being held in Cornwall, in southern England. Leaders will arrive on Friday, and meetings will get under way the following morning.
The main topic of conversation will be Covid recovery, including “a stronger global health system that can protect us all from future pandemics”.
The agenda also includes climate change and trade.
Mr Biden is expected to warn that the ongoing UK-EU trade row could imperil peace in Northern Ireland. He will call on fellow leaders to protect the gains of the Good Friday agreement.
At the end of the summit, the UK – as the host nation – will publish a document outlining what has been agreed by the leaders.
The first US-Russia summit of the Biden presidency will take place in Switzerland on 16 June.
It comes at the tail end of Mr Biden’s trip, giving the president plenty of time to hear from US allies beforehand.
The White House has indicated that he intends to cover a “full range of pressing issues” with his Russian counterpart, including arms control, climate change, Russian military involvement in Ukraine, Russia’s cyber-hacking activities and the jailing of Russian dissident Alexei Navalny.
Mr Putin threw cold water on the meeting last week, saying he hoped to improve the “extremely low level of relations” between the two countries but expected no breakthroughs.
What else will Biden be doing?
Ahead of the G7 summit, the president is set to meet Mr Johnson. The White House said the meeting would “affirm the enduring strength” of the countries’ “special relationship”.
Both leaders took part in a virtual climate action summit hosted by the US in April but have not yet met in person.