The deal was completed despite the Persian Gulf country being criticized recently by US President Donald Trump for supporting terrorism.
Pentagon Chief Jim Mattis and representatives from Qatar were set to meet Wednesday to seal the agreement, a source familiar with the deal told Reuters.
The sale seeks to increase security cooperation between the US and Qatar, the Pentagon said in a statement Wednesday.
Mattis and Qatari Minister of State for Defense Affairs Khalid al-Attiyah also discussed the current state of operations against Daesh (ISIL or ISIS), the Pentagon added.
Bloomberg News reported the deal was for 36 jets.
In November, the United States approved possible sale of up to 72 F-15QA aircraft to Qatar for $21.1 billion.
Boeing Co is the prime contractor on the fighter jet sale to the Middle East nation. Boeing declined to comment. It is unclear if this is part of the November agreement.