Washington (CNN) President Donald Trump claimed during a White House briefing on Thursday that the Food and Drug Administration had approved the "very powerful" drug chloroquine to treat coronavirus .

"It's shown very encouraging -- very, very encouraging early results. And we're going to be able to make that drug available almost immediately. And that's where the FDA has been so great. They -- they've gone through the approval process; it's been approved. And they did it -- they took it down from many, many months to immediate. So we're going to be able to make that drug available by prescription or states," Trump said

He added: "Normally the FDA would take a long time to approve something like that, and it's -- it was approved very, very quickly and it's now approved, by prescription."

: Chloroquine has not been approved by the FDA to treat the coronavirus -- and nor has any other drug, the FDA made clear in a post-briefing statement that said "there are no FDA-approved therapeutics or drugs to treat, cure or prevent COVID-19." Because chloroquine has been approved for other purposes, doctors are legally allowed to prescribe it for the unapproved or "off-label" use of treating the coronavirus if they want. But its safety and effectiveness has not been proven with regard to the coronavirus. FDA Commissioner Dr. Stephen Hahn, speaking after Trump at the briefing, said that chloroquine would be tested through a "large, pragmatic clinical trial" with coronavirus patients.

The FDA said in the statement that it is working with government and academic entities that are investigating whether chloroquine can be used "to treat patients with mild-to-moderate COVID-19 to potentially reduce the duration of symptoms, as well as viral shedding, which can help prevent the spread of disease."

Studies are underway. Hahn emphasized that this study process is necessary even though the coronavirus situation is urgent.

"We also must ensure these products are effective; otherwise we risk treating patients with a product that might not work when they could have pursued other, more appropriate, treatments," Hahn said in the statement.

Pharmaceutical company Bayer announced on Thursday that it is donating 3 million tablets of its chloroquine phosphate drug, sold under the name Resochin, to the US government.