The Athletic says Isak believes he can achieve his ambitions at Newcastle, but has postponed the possibility of signing a contract extension until the summer.
Thus, despite interest in the striker from Arsenal, Liverpool, PSG, and especially Barçelona, the player is "happy" at Newcastle and isn't thinking "about the future".
Furthermore, an offer well in excess of £100 million would be necessary to soften the club's position, which is preparing a new contract to secure the striker.
However, Isak has yet to make a decision, which won't come until the end of the season.
He said, "As for my future, it's nothing I'm really thinking about. I'm focusing on work, and now is probably the worst time to think about anything else."
Asked about the possibility of signing a new contract in the summer, he added: "I'm not thinking about the summer, but yes, we'll talk about it when the season is over."