League One side Bournemouth are understood to have agreed a fee for Fraser, who has rejected an extension to his Dons contract which expires at the end of the season.
Fraser is now heading for talks with Bournemouth after attracting interest from clubs in the Premier League and Championship earlier in the season.
Brown had previously hoped to persuade Fraser to stay at Pittodrie and is now waiting on the outcome of the 18-year-old's talks with the Eddie Howe's side.
"It is not a given he will go there," said Brown, with Bournemouth's Tuesday night FA Cup opponents Wigan Athletic having previously been linked with a bid for Fraser.
"It's clear we will be looking for more money than we'd be entitled to at the end of the season.
"What happens next is between Ryan, his agent and Bournemouth."