US Navy hospital ship USNS Mercy in central Vietnam in 2018. Linh Pham/AFP/Getty Images

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, is preparing to sign orders that could lead to the deployment of both of the US Navy’s hospital ships and a mobile hospital facility, according to two defense officials.

The two hospital ships are the USNS Mercy, currently in port in San Diego, and the USNS Comfort in Norfolk where it is undergoing maintenance. The third element that is part of the expected so-called “warning order” is a Navy Expeditionary Medical Facility, which is a mobile field hospital that has full resuscitation and emergency stabilizing surgical capability.

According to the Navy website, an EMF is “designed to be assembled and operational in 10 days,” as a self-sustaining medical facility.

Defense Secretary Mark Esper on Tuesday referred to the hospital ships noting, “We have already given orders to the Navy a few days ago to lean forward in terms of getting them ready to deploy. They provide capabilities.”

A warning order from Milley will then formalize the process and lead to decisions on calling up to active duty troops or other medical care organizations to operate the ships. Activating the EMF could lead to Seabees being called to build the hospital.

But a limiting factor remain on how all of the medical needs for ships and hospital get manned.

“All of those doctors and nurses either come from our medical treatment facilities or they come from the Reserves which means civilians and so what we have go to be very conscious of and careful of as we call up these units and use them to support the states that we aren’t robbing Peter to pay Paul,” Esper said. “What I don’t want to do is take reservists from a hospital where they are needed just to put them on a ship somewhere else where they are needed so we have to be very conscious of that.”

Esper said he had spoken to several governors about that very challenge.