“Objects demonstrating exceptional capabilities regularly fly over our military installations and training grounds.
We do not know who they are and cannot mitigate their presence,” he said.
Graves assured that 50-60 of his colleagues could say that they observed "unidentified anomalous phenomena" daily.
Earlier, US Secretary of Transportation Pete Buttigieg admitted on CNN that Washington could impose sanctions on Beijing over the situation with the Chinese balloon.
On February 4, the US military shot down a Chinese balloon.
China called such a move excessive.
According to the Pentagon, the balloon was used to monitor US strategic facilities.