The threat was conveyed by White House chief of staff Mark Meadows and reflected the Trump administration's frustration that the U.S. had lagged behind other countries in getting a COVID-19 vaccine approved, according to published reports on CNN and the Washington Post.

But Hahn disputed the description of the conversation characterized by the news.

"This is an untrue representation of the phone call with the Chief of Staff. The FDA was encouraged to continue working expeditiously on Pfizer-BioNTech's (emergency use authorization) request," Hahn said in a statement Friday afternoon. "[The] FDA is committed to issuing this authorization quickly, as we noted in our statement this morning."

In addition, it's doubtful the FDA commissioner will be fired, a White House official familiar with the conversation told CNN. The comment is more a larger signal of the president's frustration with the vaccine approval process, the person said.

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