WASHINGTON (AP) — Defense Secretary Mark Esper said Tuesday that the Pentagon will provide civilian health authorities with 5 million respirator masks and 2,000 specialized ventilators to help in a national response to the coronavirus pandemic.

Esper told Pentagon reporters that the ventilators are designed for use by deployed troops and the military will need to train civilians on how to use them. He said some may have “single-use” limitations. And he said the first million respirator masks will be made available immediately.

U.S. officials have talked about the shortage of ventilators to help treat patients with the virus.

Esper stressed that although the Defense Department is prepared to help civilian authorities in any way possible, there are limitations to the assistance and trade-offs that must be considered. “We want to be the last resort,” he said, adding that the first line of defense in fighting the virus should be state and local authorities.

Esper also said he has asked the Navy to prepare its two hospital ships — the USNS Mercy in San Diego and the USNS Comfort in Norfolk, Virginia — for deployment. He said the Pentagon will also talk with state and local leaders to see if there is any need for field hospitals.

He said the field units could be used to take the pressure off local hospitals by locating them nearby and using them to perhaps treat trauma patients. Doing so, he said, could free up hospital rooms so they could be used for infectious patients.

The Pentagon has said its hospital ships and field units are designed mainly for treating combat casualties and have areas where multiple patients are together in one room. As a result, they aren't set up to handle patients who need isolation.

Esper made clear that the Pentagon expects to be part of the COVID-19 fight for the long haul, even as it reports increasing numbers of military members being stricken by the disease. The Pentagon said that as of Tuesday morning, 36 military members had been confirmed as having the virus, up from 18 the day before. On Tuesday the Navy reported two sailors had tested positive for the virus — one aboard the USS Coronado and another aboard the USS Ralph Johnson.

Esper said he is considering activating National Guard and Reserve units to help states with planning, logistics and medical support as needed.

"As we get requests in we will look at activating, if we need to, at the federal level or using the Reserves – whatever the case may be,” he said.

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Associated Press writer Lolita C. Baldor contributed to this report.