Duncan is regarded as one of Ghana's most promising young players and has been compared Chelsea's Michael Essien.
A move to the Stadium of Light has been mooted this summer, and the 20-year-old claims he is aware of the reported interest from Wearside.
Duncan said: "I am flattered by the interest of Sunderland. I know the scout of Sunderland has been watching me.
"To be honest, though, nothing has been done and Inter will have a big say if I leave Inter or not.
"Fans compare me with Essien and if I can have half of his career I will be very happy.
"He is the best midfielder ever in Ghana. He played box-to-box, could break play up and could dictate play at the same time."