• White House chief of staff Mark Meadows told the head of the FDA to submit his resignation if the agency doesn't clear Pfizer's vaccine for emergency use by day's end, according to reports.
• The warning led FDA Commissioner Stephen Hahn and the agency to accelerate its timetable for clearing America's first Covid-19 vaccine from Saturday morning to later Friday, according to The Washington Post.
• The New York Times, Axios and Reuters also reported that Meadows told Hahn to resign if he didn't move quickly to clear the vaccine.

White House chief of staff Mark Meadows told the head of the Food and Drug Administration to submit his resignation if the agency doesn't clear Pfizer's coronavirus vaccine for emergency use by day's end, The Washington Post reported Friday.

The warning led FDA Commissioner Stephen Hahn and the agency to accelerate its timetable for clearing America's first Covid-19 vaccine from Saturday morning to later Friday, according to the Post, which cited anonymous sources.

The New York Times, Axios and Reuters also reported that Meadows told Hahn to resign if he didn't move quickly to clear the vaccine.

In a statement, Hahn called the Post's report "an untrue representation."

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

The White House did not immediately respond to CNBC's request for comment.

The reports come a day after a key FDA advisory panel voted 17 to 4 with one abstention to recommend the vaccine, which Pfizer developed alongside BioNTech, for emergency authorization. The FDA typically follows the Vaccines and Related Biological Products Advisory Committee's advice. Following the overwhelming vote, the FDA was expected to clear the vaccine as early as Friday.

Hahn said earlier in the day that the agency was "rapidly" working toward clearing Pfizer's vaccine for emergency use. "The agency has also notified the U.S. Centers for Disease Control and Prevention and Operation Warp Speed, so they can execute their plans for timely vaccine distribution," Hahn said in a joint statement with Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research.

Shortly after Hahn's remarks, President Donald Trump, who has repeatedly pushed the FDA to move quickly on the vaccine development process, told the agency in a tweet to "Get the dam vaccines out NOW."

"Stop playing games and start saving lives!!!"

While my pushing the money drenched but heavily bureaucratic @US_FDA saved five years in the approval of NUMEROUS great new vaccines, it is still a big, old, slow turtle. Get the dam vaccines out NOW, Dr. Hahn @SteveFDA. Stop playing games and start saving lives!!!

— Donald J. Trump (@realDonaldTrump) December 11, 2020

An FDA authorization would mark a record-breaking time frame for a process that normally takes about a decade. The fastest-ever vaccine development, for mumps, took more than four years and was licensed in 1967. Pfizer and BioNTech announced plans to develop a coronavirus vaccine in March and submitted an application to the FDA for emergency authorization in November.

An emergency use authorization, or EUA, isn't the same as a full approval, which can typically take months. Pfizer has only submitted two months of follow-up safety data, but the agency usually requires six months for full approval.

— CNBC's Amanda Macias contributed to this report.