Manchester United has been warned by Dutch champions against signing both Antony and Lisandro Martinez this summer.
The Eredivisie title holders said they will not allow both players to leave the club this summer.
Manchester United is preparing an offer for Martinez, with new boss Erik ten Hag keen on bringing some of his former players at Ajax to Old Trafford this summer.
Arsenal also wants to buy Martinez from Ajax and has indicated that they would be willing to bid €30 million (£25.8m) this summer.
Apart from Martinez, Manchester United is closing in on a £40m deal for Brazilian winger Antony.
But Daily Mirror reports that Ajax is not willing to let both players leave this summer, meaning that Ten Hag may need to choose from one of them.
Ajax, meanwhile, has already lost Ryan Gravenberch to Bayern Munich this summer.