Yonhap news agency says the cruiser USS Lake Champlain was engaging in training Tuesday when it collided with the 9.8-ton fishing boat off South Korea's east coast.
Yonhap cites an unidentified South Korean military official as saying the incident appears to be a minor collision and that no casualties have been reported.
South Korea's Defence Ministry has confirmed the substance of the Yonhap report but gave no further details.
The cause of the collision wasn't immediately known. About 28,500 US troops are stationed in South Korea as deterrence against potential aggression from North Korea.