Marc Cucurella has handed in a transfer request at Brighton.
The Seagulls have already rejected one bid from Manchester City for the defender and are understood to be holding out for a £50m fee for the former Barcelona player.
The 24-year-old left-back joined Brighton from Getafe last summer.
He has been identified by City manager Pep Guardiola as a replacement for Oleksandr Zinchenko, who left City to join Arsenal this summer.
Cucurella is understood to feel Brighton's asking price is unrealistic.
Asked about the defender at a news conference for the Community Shield with Liverpool on Saturday at the King Power Stadium, City manager Pep Guardiola said: "He is a Brighton player. I cannot say anything."
Pressed further on his desire to sign a left-sided defender, the City boss added: "If it is possible, yes.
"If not, we stay with what we have. We have enough players who can play there, Joao [Cancelo] can play there. Nathan [Ake].