WASHINGTON — Veterans Affairs Secretary Robert Wilkie on Wednesday defended the use of an unproven drug for the coronavirus on veterans, insisting they were never used as “test subjects” but given the treatment only when medically appropriate.

In a letter and call with major veterans organizations, Wilkie said the malaria drug hydroxychloroquine was being administered in government-run VA hospitals to virus-stricken patients only in conjunction with a physician’s advice.

But Wilkie declined to say how widely the drug was being used for COVID-19 and whether the department had issued broad guidance to doctors and patients on the use of the drug, which has been heavily touted by President Donald Trump.

The Food and Drug Administration has warned doctors against prescribing the drug for COVID-19 outside hospitals because of the risks of serious side effects and death.

“Our number one priority is keeping veterans, their families, and our staff safe and healthy,” Wilkie said in the letter.

He stressed without elaborating that the VA, the nation’s largest health care system, was adhering to FDA guidance allowing prescriptions of the drug for COVID-19 in hospitals.