Hull are seeking a much higher fee for the 21-year-old, who netted 12 goals in the Championship last term.
"There is a firm offer but we're not doing anything yet," Hull vice-chairman Tan Kesler told BBC Humberside Sport.
"It's not enough. He's such a good guy and we did what we had to do for him.
"With Keano, the most important thing is that he is from here, and he has one more final step to achieve in Hull. If he believes in that, no problems. If he doesn't believe in that, then no problems and if the offer is right we will consider it.
"I'm not saying we're considering selling him. The market is open, we'd like to hear, we'd like to talk and that doesn't mean we're going to decide.
"I'd really like him to stay one more year and take us to the play-offs, if not the promotion dream that we have."