The 17-year-old, who is also wanted by Tottenham Hotspur and Manchester United, is the second-youngest player to ever feature in the UEFA Champions League and has been capped at senior level by Croatia on three occasions.
Despite turning down Barca's initial offer for the midfielder, Mamic expects the Catalan giants to return with another.
"We have received an offer from Barcelona for Halilovic, but it was not accepted because we, the player and his family were not entirely satisfied with the terms," he told Sportski.
"The story does not stop there. Barcelona still want the transfer to happen so we will see how everything will continue.
"We would like to see Halilovic at our club for at least three years."