The Dutchman was angered by Lukaku expressing his desire his desire to play in the Champions League and win titles, combined with Everton's failure to attract the best players, as the reasons behind his decision not to sign a new contract, which his agent claimed was "99.9 per cent" done.
However, with the Belgium international having more than two years remaining on his present deal at the club, Koeman said he was not overly concerned at present.
"Of course I am not happy about that interview. If Everton is not a club with a lot of ambition I would not be manager," the manager told reporters.
"But I am not so afraid about his situation because the player has more than two years on his contract.
"Everyone knows what can happen in football but you need to respect your contract."