Reports have suggested City are weighing up a move for Fred as they look to add to their attacking options for next season.
City are in the market for a new striker having sold Carlos Tevez to Juventus and Fred is one of several names to be linked with a move to the Etihad Stadium.
The 29-year-old impressed in the Confederations Cup, scoring twice in Sunday's 3-0 final win over Spain and finishing the tournament with five goals.
When asked about the City rumour Fluminense's director of football Rodrigo Caetano told ESPN Brazil: "Fred is under contract with Fluminense, he is very happy at the club and we are very satisfied with him."
Fred admits it would have to be a "great offer" for him to leave Fluminense after joining the club in 2009 from Lyon.
"I am doing great at Fluminense and I will only leave the club if there is a really great offer," noted Fred.