Porto have attempted to warn off Chelsea by slapping an £85m price tag on Brazilian striker Hulk.
Blues boss Andre Villas-Boas recently revealed that he is interested in luring the 25-year-old to Stamford Bridge in the summer.
While the former Premier League champions are thought to be in pursuit of the hitman, Porto chairman Jorge Nuno Pinto da Costa has claimed that the only way that Hulk will be sold is if Chelsea meet the player's hefty buyout clause.
"I've said it before, we would not sell Hulk and therefore Chelsea must activate his contract," said Da Costa.
Despite the club's firm stance, Hulk's agent has claimed that the striker would consider a switch to the Premier League.
"We know there is lots of interest from Europe, but the player has told me privately Chelsea is his preferred destination," said Hulk's agent.
The frontman doesn't come to the end of his contract until 2016.
