Arsenal and Manchester United target Vitinha will only be sold if his release clause is met, according to Porto president Pinto da Costa.
Mikel Arteta's side have been heavily linked with Leicester City midfielder Youri Tielemans in recent weeks.
But Porto star Vitinha has emerged as a potential alternative as Arteta looks to bolster his midfield, which already includes Granit Xhaka, Thomas Partey and Martin Odegaard.
Reports in Portugal suggested Arsenal are the only club willing to meet the Portugal international's £35million release clause.
United are also said to be interested, with Barcelona among those attempting to secure the midfielder's services should they be able to ease financial difficulties.
Da Costa, speaking to reporters on Wednesday, revealed Porto have received an unsatisfactory bid for Vitinha, who will only be allowed to leave should his release clause be met.
"There was a concrete offer, of considerable value, for Vitinha that we did not accept," he said.
"And we referred them to the release clause, which is the only way to take our player."
Arteta is also in the market for a striker, with Gabriel Jesus and Victor Osimhen among the names being linked to the Emirates Stadium.
That is after Arsenal lost Alexander Lacazette to Lyon on a free transfer and Pierre-Emerick Aubameyang to Barcelona in January, while Eddie Nketiah is yet to agree to a new contract.
Whoever the talisman is that Arteta manages to capture, Vitinha will provide capable creative support from midfield.
The 22-year-old played 30 games in the Portuguese Primeira Liga this season, ranking second among Porto players for successful passes (1,680) and third for chances created (42).