The Argentine stopper, who did not make his country's squad for the World Cup finals, has served as back-up to David de Gea since joining the club from Sampdoria in 2015.
"I'm staying at Manchester United for now. [United manager] Mourinho worked hard for my renewal until 2022. I can't leave him now," Romero told TyC Sports.
"If United wants to sell me, if they have an offer that is useful for the club, they will sell me. But I don't think that would happen."
Romero was in contention for Argentina's World Cup squad, but missed out due to suffering a knee injury before the team was announced.