Porto president Jorge Nuno Pinto da Costa is adamant Chelsea target Alvaro Pereira will not be leaving for less than his release clause.
Chelsea boss Andre Villas-Boas is keen to raid his former club to add the Uruguay international to his squad before the transfer window closes.
Pereira, who can play at left-back or on the left of midfield, has already been the subject of a failed £15million bid from the Blues.
Pinto da Costa says he quickly rejected the offer and Villas-Boas has acknowledged the two clubs are currently far apart in their valuations of Pereira.
The player has a €30million (£26.5m) release clause and Pinto da Costa is adamant Pereira will not be leaving until that figure is met.
"Chelsea made us an offer for Pereira, but it took just 30 seconds to turn it down," said Pinto da Costa.
"Every player who has an escape clause in his contract can leave if somebody makes us an offer that matches that fee.
"But for Pereira, that escape clause is €30million."