WASHINGTON — The United States will double the number of COVID-19 vaccine doses it is donating to the global inoculation effort, President Joe Biden announced Wednesday.

The commitment will bring to more than 1 billion the total number of doses the U.S. has pledged to other countries in hopes of bringing the pandemic to a close and preventing dangerous variants from emerging. All of the donations are scheduled to be shipped by this time next year.

“This is a global tragedy,” Biden said during a virtual summit on COVID-19 that was convened during the United Nations General Assembly. “And we’re not going to solve this with half measures.”

The highly contagious delta variant, which was first detected in India, has underscored the danger of uncontrolled spread, ripping through unvaccinated communities and causing another surge in deaths.

“To beat the pandemic here, we need to beat it everywhere,” Biden said.

The president urged other wealthy nations to follow the U.S.’ lead and increase their own donations, calling it “an all-hands-on-deck crisis.”

So far, the U.S. has shipped 160 million doses. The vaccines are being provided “free of charge, no strings attached,” said a senior administration official who was not authorized to speak publicly before Wednesday’s announcement.

The U.S. has been under pressure to contribute more vaccine to other countries, especially as administration officials prepare to make booster shots available this year — meaning some Americans will probably receive three doses when many people in poor countries haven’t received one.

U.N. Secretary-General Antonio Guterres said Tuesday that the uneven vaccination distribution is “a moral indictment of the state of our world.” More than 70% of the 5.7 billion vaccine doses administrated globally have gone to just 10 countries, according to the World Health Organization.

Dr. William Parker, a medical ethicist and assistant professor of pulmonary and critical care medicine at the University of Chicago, said shipping doses overseas “would do far more good” in terms of saving lives.

A panel that advises the Food and Drug Administration last week rejected a plan that would have made booster shots of Pfizer-BioNTech’s COVID-19 vaccine available to most Americans, in part because it was unclear how the third dose would substantially contribute to controlling the pandemic. The panel backed giving extra shots to those over the age of 65 or who are immunocompromised.

Giving a healthy adult a booster to “prevent cold, mild or asymptomatic infections at the expense of costing someone in a low-income country their life to me seems unethical,” Parker said.

Officials defended the administration’s plans, saying the country will be donating three doses to other countries for each one administered to a patient in the United States.

In his speech Tuesday to the U.N. — his first as president — Biden described the pandemic as a collective challenge.

“We’re mourning more than 4.5 million people, people of every nation, from every background,” he said. “Each death is an individual heartbreak, but our shared grief is a poignant reminder that our collective future will hinge on our ability to recognize our common humanity and to act together.”

Dr. Walter A. Orenstein, associate director of the Emory Vaccine Center, said producing enough vaccines will be challenging.

“Manufacturing capacity has generally been adequate for the vaccines we routinely use,” Orenstein said, because not every person in the world has needed to be inoculated against every disease. But now, the whole world needs this vaccine, and manufacturing capacity is not able to meet this demand, he said.

“It’s not like overnight you can just rev up and vaccinate the entire world,” he said. The industry has never had to produce “anywhere near the number of doses we need” to combat COVID-19, he said.

Biden said his administration is working with other countries to increase their own manufacturing capacity. He said plans are underway to produce 1 billion doses in India and another 500 million doses in South Africa next year.