President Joe Biden will announce Wednesday the US plans to donate an additional 500 million Pfizer-BioNTech Covid vaccines to the rest of the world, bringing its total commitment to 1.1 billion, officials said.

Biden will relay the news at a virtual summit to be held on the margins of the United Nations General Assembly, where he will challenge world leaders to vaccinate 70 percent of every country by September 2022.

The donations are being made "free of charge, no strings attached," a senior administration official said ahead of the meeting.

"For every one shot we have administered in this country to date, we are now donating three shots to other countries," she added.

In his first speech to the UN as president on Tuesday, Biden told delegates that the United States had put more than $15 billion towards the global Covid response and shipped more than 160 million doses to other countries.

The United States and other wealthy countries have been criticized by the World Health Organization for their plans to roll out booster shots for elderly and high-risk populations, while much of the world faces a severe shortage in doses.

But the administration official said: "We're proving that you can take care of your own, while helping others as well."

President Joe Biden is set to announce the United States plans to donate an additional 500 million Pfizer-BioNTech Covid vaccines to the rest of the world
President Joe Biden is set to announce the United States plans to donate an additional 500 million Pfizer-BioNTech Covid vaccines to the rest of the world GETTY IMAGES NORTH AMERICA / Ethan Miller

Despite the development of safe and highly effective vaccines in record-breaking time, huge disparities exist between countries with ample supply and others that have barely begun their immunization campaign.

Just 3.6 percent of Africa's eligible population has been inoculated -- compared with an average of more than 60 percent in Western Europe.

Biden has invited heads of state, leaders of international organizations, private sector philanthropies, and NGOs for the summit, which begins around 11:00 am Eastern Time (1500 GMT).

"The president will call on world leaders to elevate the global level of ambition to end the Covid pandemic in 2022, and to build back better health security to prevent and prepare for future pandemics," said a second US official.

Washington will seek to rally the world around three goals: increasing vaccine supply; saving lives now by resolving the oxygen crisis and access to testing, medicine and therapeutics; and lastly improving future preparedness.

On vaccines, Biden will set an "ambitious target, which will require all countries to step up, so that every country, including low income and low middle income countries can achieve 70 percent vaccination before UNGA (United Nations General Assembly) of next year," the official said.

The summit will include sessions chaired by Biden and Vice President Kamala Harris, and will be attended by WHO chief Tedros Adhanom.

While the latest global wave peaked in late August, the virus continues to spread rapidly, particularly in the United States which is officially the worst-hit country.

Some 4.7 million have died since the outbreak began in China in December 2019, according to an AFP tally from official sources.