The recommendations follow reviews of 11 US military sites by the Suicide Prevention and Response Independent Review Committee (SPRIRC), which conducted more than 2,700 interviews with military personnel and civilian staff.

The Pentagon says more than 500 servicemembers and 200 of their dependents took their own lives -- most using firearms -- during 2021, the most recent year for which data has been released.

"Every day, the United States military loses brave men and women to suicide. Each death is a devastating loss for families, fellow service members, and our entire force," Austin wrote in a memo on the recommendations.

"All of us in the Defense Department need to do more to prevent these tragedies," he said in the document, which was dated September 26 but released on Thursday.

The recommendations fall into five broad categories: increasing quality of life for service members, improving the delivery of mental health services, addressing the stigma around seeking help, revising suicide prevention training, and improving firearm safety.

Austin's memo notes that "approximately 70 percent of service members who die by suicide use firearms as the primary mechanism of injury," and says "secure storage practices for firearms have been proven to save lives."

To address this, the military will take steps including offering incentives for troops for the purchase of secure firearms storage, adding content on safe storage to firearms proficiency training, and providing additional storage options on bases.

However, other gun-related recommendations -- including waiting periods for the purchase of guns and ammunition on Department of Defense property, as well as raising the minimum age for both to 25 -- were not approved.

Speaking about the age restriction, Elizabeth Foster -- the executive director of the Office of Force Resiliency -- told journalists that legal concerns played a role.

"Ultimately we determined that there are some significant legal barriers to implementing that recommendation at this time," she said.

Firearm regulation is a highly contentious issue in the United States, with conservative politicians opposing most restrictions aimed at curbing the frequent gun violence plaguing the country.