The United States plans to purchase and donate 500 million doses of the Pfizer-BioNTech COVID-19 vaccine for use overseas, a person familiar with the expected announcement confirmed.

The donations could be a boon to COVAX, an initiative backed by the World Health Organization to distribute vaccines to low- and middle-income countries based on population. The Pfizer vaccine requires two doses, so the U.S. donation will be able to fully vaccinate 250 million people.

President Joe Biden is expected to announce the strategy during his first trip abroad for a meeting of the G-7 wealthy democracies this week in Britain. Biden arrived at Royal Air Force Mildenhall Wednesday night where he addressed U.S. servicemembers before traveling to Cornwall for the G-7 meeting.

The U.S. has faced pressure from global health advocates, the WHO, foreign nations and progressive Democrats in Congress to share its glut of vaccines with the world, as millions of vaccines near their expiration dates in the U.S.

The U.S. and European Union plan to jointly announce the goal of vaccinating “at least two-thirds of the world’s population by the end of 2022,” according to a draft communique obtained by Reuters.

Vaccinating 70 percent of the world with two-dose vaccines would require roughly 11 billion doses.

“I applaud President Biden’s momentous decision to provide 500 million doses of the Pfizer vaccine to dozens of nations in need — including India, Brazil, and other places where COVID-19 is surging. By doing so, we are not only taking a critical step in unleashing the resources necessary to defeat this deadly virus abroad, but we are protecting people at home while restoring our place as a global leader and international partner,” House Progressive Caucus Chair Pramila Jayapal, D-Wash., said in a statement. “At the heart of today’s announcement is a powerful recognition that whether you live in America or around the world, your future is intertwined with mine — that we are all better off when we are all better off.”

Tom Hart, the acting CEO of the ONE Campaign, was among those praising the decision ahead of Biden’s announcement.

“We won’t end this global pandemic anywhere unless we beat it everywhere. Donating doses to COVAX will save lives, reduce the spread of variants, and help reopen the global economy,” Hart said in a statement. “We urge other G7 countries to follow the US’ example and donate more doses to COVAX. If there was ever a time for global ambition and action to end the pandemic, it’s now.”

UNICEF has called on the G-7 countries to donate 20 percent of their existing supply this summer, which the global nonprofit says would free up 153 million doses and still allow the countries to inoculate their own populations.

The plan to donate Pfizer doses was first reported by The New York Times. 

Peter Maybarduk, an advocate for global vaccine access with Public Citizen, called the move a “very positive development.”

The White House had previously said it would donate 80 million doses by the end of the month and released a plan for allocating 25 million, but vaccines have been held up by a manufacturing debacle at a subcontractor for AstraZeneca and Johnson & Johnson called Emergent BioSolutions. These doses are undergoing a safety inspection by the Food and Drug Administration.

Still, the development is unlikely to completely resolve an ongoing debate around temporarily lifting intellectual property rights so that competing plants can produce more doses, a move the U.S. supports but the European Union opposes. 

“President Biden and other leaders have underestimated their power to set terms with the vaccine makers and coordinate production at massive scale. Billions of people awaiting a path out of the pandemic urgently need this to change,” Maybarduk said.

A major supplier of the COVAX facility, the Serum Institute of India, halted shipments when that country began to experience a historic wave of COVID-19 infections and deaths.