China says the US has "hyped up" the controversy over the seizure of an underwater drone.
The submarine was collecting scientific data in the disputed South China Sea when it was taken by a Chinese warship.
US President-elect Donald Trump tweeted to say the action is "unprecedented."
China steals United States Navy research drone in international waters - rips it out of water and takes it to China in unprecedented act.
— Donald J. Trump (@realDonaldTrump) December 17, 2016
China now says it will return the craft.
But it has called on the US to stop surveillance missions in its territorial waters.
