The defense secretary later clarified that he wouldn't "defy" a ruling from the Supreme Court.
A war with China would include fierce naval battles and require the Air Force to take out enemy ships with weapons such as Quicksink.
The defense secretary took issue with multiple questions, at times talking over Senators at the hearing.
Air Force officials say the E-7 must replace its aging E-3 AWACS planes and would be needed even when space-based ISR capabilities are in orbit.
