Liverpool have been strongly linked with a move for the left-back, but talks have reportedly broken down over the transfer fee.
Castro has maintained his stance and claimed that Moreno will remain at Sevilla unless his release clause is activated, with the figure believed to be in the region of £20m.
"It's true that there is interest from several teams," Castro told ABC.
"One of these teams is Liverpool, but there haven't been any formal talks over his signing. We decide his price. If Alberto Moreno want to stay, he'll stay. If Liverpool pay his price, he'll leave."
Moreno was part of Spain's initial 30-man squad for the World Cup this summer.