The 23-year old striker has been tracked by the likes of Tottenham and Liverpool recently with United also believed to be very keen.
Reports have stated that the Red Devils are pondering a January move for Damiao but Luigi says that they will have to meet his buyout clause if they want to purchase the Brazilian talent.
"We aren't talking about a small team. We are talking about Internacional," Luigi told Zero Hora.
"Now, Leandro Damiao only leaves if the buyout fee is paid."