White House Chief of Staff Mark Meadows wears a protective mask as he leaves Senate Republican luncheon in the Hart Senate Office Building in Washington, DC on Oct.21. Stefani Reynolds / Getty Images

White House Chief of Staff Mark Meadows is due to meet with FDA Commissioner Dr. Stephen Hahn, as President Donald Trump asked privately why his agency has not yet granted an emergency for Pfizer’s coronavirus vaccine, according to two sources.

Meadows invited Hahn to a progress update over the weekend. Hahn called for their meeting, according to a source, but the White House informed him that the chief of staff preferred to meet in person. This appears to have raised concerns within the FDA that the meeting may be strained, which has led Hahn to give Axios a statement tonight defending the FDA’s timeline.

“Let me be clear – our career scientists have to make the decision and they will take the time it takes to properly make this important decision,” said Hahn.

Pfizer filed for the EEA on November 20.

Authorization in case of emergency from the FDA is not the same as full approval, but allows products to be used in certain circumstances before all of the evidence for approval is available, as suggested by previous CNN reports.

The FDA previously announced that it would schedule a meeting of its external advisory panel to discuss Pfizer and BioNTech’s application for emergency use approval for a coronavirus vaccine on December 10th.

But Trump is privately frustrated with how long the process is taking, sources told CNN. He has proudly and publicly admitted that he was pressuring the FDA to move faster.

“It could have taken four or five years to do this,” Trump told reporters of progress with vaccination for Thanksgiving. “Ordinarily, it would have probably taken four or five years just to get through the FDA. We pushed it very hard.”

It is not clear how the Meadows-Hahn meeting will go until it takes place. There was already a suspicion of the FDA among Trump’s closest advisors and career scientists before the FDA issued public statements on Monday night about the meeting.