President Joe Biden announced Wednesday that the United States is doubling its purchase of Pfizer's COVID-19 shots to share with the world to 1 billion doses, and he called on other high-income nations to step up their efforts to combat the pandemic.

Biden made the announcement at the start of the global vaccination summit that he convened virtually Wednesday on the sidelines of the U.N. General Assembly. He also announced the U.S. will donate an additional $370 million toward administering vaccines around the world.

“This is an all-hands-on-deck crisis,” the president said. “And the good news is we know how to beat this pandemic: vaccines, public health measures and collective action.”

In previewing the meeting Tuesday, senior administrations officials told reporters that Biden would also embrace the goal of vaccinating 70% of the global population within the next year, although he did not mention that in his opening remarks.

World leaders, aid groups and global health organizations are growing increasingly vocal about the slow pace of global vaccinations and the inequity of access to shots between residents of wealthier and poorer nations.

More than 5.9 billion COVID-19 doses have been administered globally over the past year, representing about 43% of the global population. But there are vast disparities in distribution.

While more than a dozen countries, including Portugal, the United Arab Emirates and Canada, have fully vaccinated at least 70% of their populations, many other nations, especially in Africa, have inoculated tiny fractions of their people, and many others are still well below the rate needed to considerably slow the virus’ spread.

The U.S. purchase, according to the White House, will bring the total U.S. vaccination commitment to more than 1.1 billion doses through 2022. At least 160 million shots supplied by the U.S. have been distributed to more than 100 countries, representing more donations than the rest of the world combined.

“Put another way, for every one shot we've administered to date in America, we have now committed to do three shots to the rest of the world,” Biden said.

“We … know that to beat the pandemic here, we need to beat it everywhere,” the president added. “And I made and I'm keeping the promise that America will become the arsenal of vaccines, as were the arsenal for democracy during World War II.”

The latest purchase reflects only a fraction of what will be necessary to meet a goal of vaccinating 70% of the global population — and 70% of the citizens of each nation — by next September’s U.N. meeting. It's a target pushed by global aid groups.

Biden urged other high-income countries to deliver on their own vaccine pledges. He also said the U.S. and European Union have launched a new partnership to work more closely together to expand global vaccinations.

The president said he wants nations to commit to donating, not selling, the shots to poorer countries and for the gesture to come with no political strings attached. Biden said another goal of his is to dramatically increase vaccine manufacturing capacity around the world.

He also called for help in addressing oxygen shortages in hospitals; making COVID-19 treatments, tests and masks more accessible; and improving health care infrastructure to make the world more resilient to future pandemics.

The American response has come under criticism for being too modest, particularly as the administration advocates for providing booster shots to tens of millions of Americans before vulnerable people in poorer nations have received even a first dose.

“We have observed failures of multilateralism to respond in an equitable, coordinated way to the most acute moments. The existing gaps between nations with regard to the vaccination process are unheard of,” Colombian President Iván Duque said Tuesday at the United Nations.

In remarks at the U.N., Biden took credit on Tuesday for sharing more than 160 million COVID-19 vaccine doses with other countries, including 130 million surplus doses and the first installments of more than 500 million shots the U.S. is purchasing for the rest of the world.’

Other leaders made clear in advance it was not enough.

Chilean President Sebastian Piñera said the “triumph” of speedy vaccine development was offset by political “failure” that produced inequitable distribution. “In science, cooperation prevailed; in politics, individualism. In science, shared information reigned; in politics, reserve. In science, teamwork predominated; in politics, isolated effort,” Piñera said.

The World Health Organization says only 15% of promised donations of vaccines — from rich countries that have access to large quantities of them — have been delivered. The U.N. health agency has said it wants countries to fulfill their dose-sharing pledges “immediately” and make shots available for programs that benefit poor countries and Africa in particular.

COVAX, the U.N.-backed program to ship vaccines to all countries has struggled with production issues, supply shortages and a near-cornering of the market for vaccines by wealthy nations.

The WHO has urged companies that produce vaccines to prioritize COVAX and make public their supply schedules. It also has appealed to wealthy countries to avoid broad rollouts of booster shots so doses can be made available to health care workers and vulnerable people in the developing world. Such calls have largely gone ignored.

COVAX has missed nearly all of its vaccine-sharing targets. Its managers also have lowered their ambitions to ship vaccines by the end of this year, from an original target of some 2 billion doses worldwide to hopes for 1.4 billion now. Even that mark could be missed.

Speaking later in the summit, Vice President Kamala Harris focused on efforts to prevent or quickly respond to future pandemics.

She said American and Italian officials have worked together on the issue, analyzing reports and talking to experts, who have said there is not enough funding to adequately prepare for future biological threats. 

Harris called for the creation of a financial intermediary fund at the World Bank to contribute to disease surveillance, vaccine development, vaccine delivery and other initiatives for countries around the world. 

The vice president promised the U.S. would donate at least $250 million to start the fund, adding that the Biden administration is asking Congress to approve an additional $850 million. Harris said the goal is for the fund to launch with $10 billion.

“This pandemic caught us off-guard, and it should not have,” she said. “We have learned the cost of failing to prepare. Every death, we have learned all too much the seriousness of that cost, and it is time then to act.”

Harris also said that there is an “important role and responsibility for the private sector” to assist in planning for future pandemic threats as well.

“Generations from now, I believe we will all be able to look back to this very moment, at the start of this new era, as the moment when our world joined together to realize a better future, a future in which all nations have equal capacity to prevent, detect and respond to biological threats and are equally held to account,” the vice president said.