President Donald Trump and the nation’s top infectious disease expert differed at a briefing Friday over whether an antimalarial drug would effectively treat COVID-19.

Trump said he hoped the drug, hydroxychloroquine, would be effective in treating the virus that has been labeled a worldwide pandemic. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, cautioned that it is too early to make predictions.

[Health industry scrambles for funding in third coronavirus bill]

Trump acknowledged his thoughts were based on “just a feeling” he had, calling himself “a smart guy,” and said he hoped the drug could treat the new coronavirus. The drug is not currently in clinical trials to treat COVID-19.

“I am a man that comes from a very positive school when it comes to, in particular, one of these drugs, and we’ll see how it works out,” Trump said.

Fauci said that the drug has not been tested as a COVID-19 treatment in a controlled clinical trial, so you can’t make definitive statements about its effectiveness. He sought to minimize the differences between what he and Trump said.

“The president feels optimistic about something,” he said, noting that he approaches the issue from a scientific perspective. “What I’m saying is that it might be effective. I’m not saying that it isn’t.”

The disagreement came during a lengthy news conference on Friday, in which Trump made several policy announcements, including that the nation’s southern border with Mexico would be closed to all nonessential travel and that the administration would waive interest on federally held student loans for at least the next 60 days.

Trump said he invoked the Defense Production Act on Thursday night, but he did not detail whether the administration had directed certain companies to manufacture products that health care providers need. The automaker General Motors is one company he named that he said will manufacture ventilators. He suggested that other car manufacturers have volunteered to produce additional medical equipment.

Trump also pushed back on the notion that Americans cannot get tested for the virus, despite reports that tests are still difficult to access in many parts of the country.

Health and Human Services Secretary Alex Azar said the department is establishing a task force to answer labs’ questions about getting and using supplies for tests. He suggested labs may not know about alternative supplies they can use or access.

Fauci took a different stance than Trump about how easy it is to get a test, although the NIH scientist acknowledged that testing capacity has improved in recent days.

“We are not there yet because otherwise, people would be never calling up saying they can’t get a test,” he said.