The US says it expects its civilian aircraft to observe China's rules in an air defence zone in the East China Sea.
A US statement said this did not mean the US accepted China's requirements in the zone covering territory claimed by China, Japan, Taiwan and South Korea.
China wants all aircraft there to file flight plans and identify themselves.
The US, Japan and South Korea say they have flown military aircraft in the area unannounced. But China said it scrambled fighter jets on Friday.
The move was to monitor US and Japanese aircraft in the zone.
'Firm but calm'
The air defence identification zone (ADIZ) covers a vast area of the East China Sea, including a group of islands claimed by Japan, China and Taiwan.
South Korea claims a submerged rock, known as Ieodo, also within the zone.
The establishment of the ADIZ has caused widespread anger, with the US state department calling it "an attempt to unilaterally change the status quo in the East China Sea" which will "raise regional tensions and increase the risk of miscalculation, confrontation and accidents".
But on Friday, the state department said the US government "generally expects that US carriers operating internationally will operate consistent with Notams [Notices to Airmen] issued by foreign countries".
