(CNN) White House chief of staff Mark Meadows is scheduled to meet with Food and Drug Administration Commissioner Stephen Hahn in the West Wing Tuesday, as President Donald Trump has privately demanded to know why the agency hasn't granted emergency use for Pfizer's coronavirus vaccine yet, according to two sources.
Meadows summed Hahn for a progress update over the weekend. Hahn requested their meeting happen over the phone, one source said, but was told by the White House that the chief of staff preferred to meet in person. That appears to have led to concern within the FDA that the meeting could become tense, leading Hahn to issue a statement to Axios Monday night defending the FDA's timeline.
"Let me be clear -- our career scientists have to make the decision and they will take the time that's needed to make the right call on this important decision," Hahn said in the statement.
A person familiar with the meeting tells CNN that Hahn is prepared to explain to the President's team that the decision about granting the emergency use authorization is not up to him. The review is conducted by career scientists and not a decision he makes on his own.
Pfizer applied for the emergency use authorization November 20. Emergency use authorization from the FDA is not the same as full approval but allows products to be used under particular circumstances before all the evidence is available for approval, according to previous CNN reporting. The FDA has previously said it has scheduled a meeting of its outside advisory panel to discuss Pfizer and BioNTech's application for emergency use authorization for a coronavirus vaccine for December 10.
But Trump has become privately frustrated over how long the process is taking, sources told CNN. He has proudly and publicly admitted to pressuring the FDA to move faster.
"It could have taken four or five years to do this," Trump told reporters about vaccine progress on Thanksgiving. "Normally, it probably would have taken four or five years, just getting it through the FDA. We pushed it very hard."
Amid complaints from the President that the FDA is working too slowly, White House press secretary Kayleigh McEnany said on Fox News Tuesday that the agency is working "around the clock" but said Trump "will never apologize for putting the fire under these agencies."
"We want a safe vaccine, absolutely. We also want a fast one because lives are at stake and a vaccine by the end of the year is key and paramount," McEnany said.
It's not clear how the meeting between Meadows and Hahn will go until it takes place. A sense of distrust between Trump's closest advisers and career scientists on the FDA already existed before the FDA issued public statements about the meeting Monday night.
"The FDA has been preparing for the review of EUAs for Covid-19 vaccines for several months and stands ready to do so as soon as an EUA request is submitted," Hahn said in a statement shortly after Pfizer applied for emergency use authorization for the vaccine in late November. "While we cannot predict how long the FDA's review will take, the FDA will review the request as expeditiously as possible, while still doing so in a thorough and science-based manner, so that we can help make available a vaccine that the American people deserve as soon as possible."