President Joe Biden announced that he has reached an agreement to purchase an additional 200 million coronavirus vaccine doses, a boost that means the U.S. will have enough supply to fully vaccinate 300 million Americans by the end of summer or beginning of fall.

“This is a wartime undertaking. It’s not hyperbole,” Biden said during remarks on the COVID-19 pandemic at the White House.

Biden outlined the new purchase plans along with an increase in the weekly vaccine allocation to states, tribes and territories from 8.6 million doses to a minimum of 10 million doses over the next three weeks.

The additional purchases would raise the U.S. vaccine supply from 400 million doses to 600 million doses, ensuring that the country will eventually have two shots for nearly every American.

The Department of Health and Human Services is also planning to provide states, tribes and territories with allocation estimates for the upcoming three weeks instead of the one week look-ahead they previously received, Biden said.

“This is going to help make sure governors, mayors and local leaders have greater certainty around supply, so they can carry out their plans to vaccinate as many people as possible,” he said.

The boost of 1.4 million weekly allocations will primarily be supplied by Moderna’s vaccine, one of two authorized for emergency use in the U.S. Pfizer, which makes the second authorized vaccine, announced earlier Tuesday it was ahead of schedule on fulfilling the 200 million doses the U.S. purchased last year.

Each of the vaccines requires two doses. A second shot should be administered about three or four weeks after the first, depending on which vaccine was given.

The announcement comes after several states have reported vaccine and supply shortages while tens of thousands of people who managed to get appointments for a first dose have complained of cancellations.

Biden has issued a flurry of execution actions related to COVID-19 and laid out a 198-page plan that includes a campaign to meet his pledge of administering 100 million vaccine shots in 100 days, expanding access to testing, requiring masks on most forms of transportation and providing relief to states and cities still struggling to contain the spread of the virus.

The plan’s success relies on Congress quickly acting to approve the president’s $1.9 trillion COVID-19 relief package, an ambitious proposal that some GOP lawmakers remain sceptical about.

Biden again warned that coronavirus cases would continue to climb, noting the death toll could top 500,000 by the end of next month, but remained confident in his administration’s COVID-19 plan.