The directive for all 1.3 million service members to get shots in their arms comes one day after President Biden urged all federal employees to get vaccinated.
In a speech last week, Biden said he was directing the Defense Department to examine how to make the COVID-19 vaccine mandatory.
The Department of Justice was also asked by the president to look into the legality of mandating for the military a vaccine that has yet to be approved by the Food and Drug Administration.
DOJ officials said a vaccine mandate would require a presidential waiver.
Officials told Fox News that Austin will make his recommendation to the White House tomorrow, and the formal announcement is expected to come Friday. About 64% of active-duty forces are fully vaccinated. Among all U.S. adults, about 70% have received at least one shot.
Last week, Biden said federal employees and on-site contractors would be required to get the vaccine or be subject to regular testing.
The requirement affected the Defense Department’s civilian employees but did not extend to active-duty service members. The upcoming application to active-duty service members was first reported by the New York Times.
The Centers for Disease Control and Prevention has reported a more than 64 percent increase in the number of coronavirus cases confirmed over the last seven days – bringing caseloads back on par with figures reported in mid-February.
Biden also warned that the U.S. could see increased restrictions as the highly contagious delta variant has surged nationwide, though he has yet to detail those limitations.
CDC Director Rochelle Walensky told Fox News on Friday that the administration is looking into the possibility of a vaccine mandate in an effort to bolster vaccination rates.
Roughly 50 percent of the U.S. is vaccinated, and 58 percent have received at least one dose of the vaccine.
The White House confirmed last week it is not considering another economic shutdown.
Brianna McClelland contributed to this report.