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 delivered 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”.