The Pentagon is moving to make COVID-19 vaccinations mandatory for all department employees.

On Monday, Lloyd Austin, United States Secretary of Defense, said in a memo to employees, “To defend this Nation, we need a healthy and ready force.”

“I strongly encourage all DoD military and civilian personnel — as well as contractor personnel — to get vaccinated now and for military service members to not wait for the mandate,” he added.

The Department of Defense cannot take the unilaterally because the Food and Drug Administration (FDA) has not yet approved the vaccine, according to NPR. The move would require a presidential waiver, which Austin plans to ask for by mid-September.

John Kirby, Assistant to the Secretary of Defense for Public Affairs, told reporters Monday that after getting a presidential waiver, “individual services would draft plans for implementing a mandate within each military branch.”

If the FDA gives full approval to the Pfizer-BioNTech vaccine before then, Austin has the authority to implement a mandate himself, per the news outlet.

In a statement released by the White House in tandem with the Pentagon memo, officials said President Joe Biden strongly supports mandating the vaccine.

“Being vaccinated will enable our service members to stay healthy, to better protect their families, and to ensure that our force is ready to operate anywhere in the world,” Biden said.

Kirby said the spread of the highly contagious Delta variant was a factor in the plan, as the number of cases has increased.

Kirby also said if Austin “needs to move at sooner than this timeline, then he’ll do that.” He said about 73% of active-duty service members have received at least one dose, with 62% fully vaccinated.

“We continue to want to appeal to a sense of teamwork among the unvaccinated service members,” he said, telling service members, “it’s your opportunity to contribute to the health and readiness of your teammates.”

Kirby said the military already requires some 17 vaccines for service members. The Pentagon move follows Biden’s announcement last month that all federal employees and contractors will need to confirm they are vaccinated or be tested once or twice a week for the virus, according to NPR.