The Pentagon has released new details on an expanded halt-movement order that will force tens of thousands of troops deployed overseas to stay there until the spread of a deadly global pandemic begins to slow.

Defense Secretary Mark Esper on Wednesday enacted a 60-day overseas travel prohibition for troops, their accompanying family members and Defense Department personnel. The new rules, which expand on existing travel bans, essentially bar all U.S. personnel from any international travel.

This means those scheduled to return from deployments or overseas tours, rotations and exercises could be stuck in place until late May.

In a statement announcing the new order, defense officials said the move is meant to help prevent the spread of COVID-19, the illness caused by the highly contagious coronavirus, and ultimately protect U.S. personnel and "preserve the operational readiness of our global force."

"Building upon previously enacted movement restrictions governing foreign travel, permanent change of station moves, temporary duty and personal leave, this stop movement order will also impact exercises, deployments, redeployments and other global force management activities," it states. "Approximately 90,000 Service Members slated to deploy or redeploy over the next 60 days will likely be impacted by this stop movement order."

Related: SecDef Orders 60-Day Halt to Overseas Travel for All Troops and Families: Report

Reuters first reported Esper's new order on Wednesday. He told the outlet the unprecedented restrictions had to be taken to help stop the spread of the virus, which has already affected 227 service members across the four military branches.

"The purpose is to make sure that we're not bringing the virus back home, infecting others -- that we're not spreading it around the military," Esper told Reuters.

There will be some exceptions to the policy, including for military units scheduled to leave Afghanistan. As part of the agreement to drawdown U.S. forces there, defense officials said troops will still be allowed to leave that country.

Other exceptions will include troops returning from a deployment aboard a Navy ship, those traveling for medical treatment and those already in transit. Service members or Defense Department civilians who are currently on a temporary duty assignment will also be allowed to return, according to the release.

Units embarked on Navy vessels will have to have been in transit for at least 14 days since their last stop, the policy adds.

As coronavirus cases continue to spread among the ranks, top health leaders told reporters on Wednesday the military must take steps to help stop it. That includes new health-protection conditions on every base, which were raised to the second-highest level worldwide on Wednesday.

"Our curve is not flattening," Air Force Brig. Gen. Paul Friedrichs, the Joint Staff surgeon, said of the rising coronavirus cases across the force.

The military has also restricted travel for most troops inside the U.S. and its territories. Those rules, which affect families' permanent change of station moves and other policies, remain in effect.

-- Gina Harkins can be reached at gina.harkins@military.com. Follow her on Twitter @ginaaharkins.

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