President Joe Biden announced Thursday that his administration had signed contracts for an additional 200 million doses of Covid-19 vaccine, bringing the US total to 600 million.

“We just signed the final contracts for 100 million more Moderna and 100 million more Pfizer vaccines just this afternoon,” said Biden on Thursday during a tour of the National Institutes of Health in late July.

The Washington Post reported the news first. Previously, White House Chief of Staff Ron Klain appeared to confirm the news and retweet the Post story from his official White House Twitter account.

Since both Pfizer and Moderna approved vaccines require two doses three to four weeks apart, a total of 600 million doses would be enough to vaccinate 300 million people.

Biden is trying to accelerate the pace of vaccination in the US after a slower-than-expected rollout under the administration of former President Donald Trump. Around 34.7 million out of around 331 million Americans have received at least their first dose of a Covid vaccine, according to the Centers for Disease Control and Prevention. And 11.2 million of those people have already got their second shot.

The schedule for delivering the additional doses was not immediately clear.

Each company will leverage US-based manufacturing capabilities to “fill, finish, and ship vials while the bulk goods are manufactured,” according to a separate statement from the Department of Health and Human Services.

Pfizer has already signed a contract with the US to supply 200 million cans. The company announced earlier this month that it plans to complete these shipments by May, earlier than originally forecast in July. Moderna also has a US contract for 200 million cans.

States have complained that the demand for vaccines is exceeding supply. The government previously stated that it is using the Defense Manufacturing Act to help Pfizer meet its manufacturing goals for its vaccine.

In addition to securing more doses for states, the Biden government is using the military to aid in the administration of doses and establishing mass vaccination centers in the United States.

On Wednesday, the government announced it would work with Texas officials to build three new community vaccination centers in Dallas, Arlington and Houston. A few days earlier, the government had announced that it would send troops on active duty to California to help vaccination centers for Covid-19 employees.

U.S. officials also hope vaccine supplies will increase after Johnson & Johnson’s Covid-19 vaccine is emergency approved by the Food and Drug Administration, which could happen as early as this month. The FDA scheduled a meeting of its Advisory Committee on Vaccines and Related Biological Products on February 26th to discuss the vaccine. The US could approve the vaccine the next day.

The Department of Health and Human Services announced in August that it had signed a deal with Janssen, J & J’s pharmaceutical subsidiary, worth approximately $ 1 billion for 100 million doses of its vaccine. The deal gives the federal government the opportunity to order another 200 million cans, according to the announcement.