The Scottish champions remain keen to add the Dundee United forward to their attacking lineup.
The Turkish player scored 16 times and created 9 goals last season as the Terrors finished in 5th place in the Scottish Premiership - similar figures to his first campaign at Tannadice Park.
It has meant the forward has been linked with several clubs this summer, with Wigan also having bid for his services earlier in the window only for the player to reject a move to League One, according to BBC Sport.
Celtic have been keen to recruit Ciftci alongside the likes of former Dundee United players Stuart Armstrong and Gary Mackay-Steven, both of whom joined over the course of last season.
Several bids for the player have already been rejected, and the Evening Times are saying the Scottish champs will have to pay as much as £2 million to secure their target.
Dundee United holding out for a big fee
With the young striker top scoring for Dundee United in the last two seasons, it is no surprise former Bhoy McNamara is holding out for as large a fee as possible for Ciftci.
The Terrors were accused of letting both Armstrong and Mackay-Steven go to Celtic on the cheap, and with Ciftci about to enter the last year of his contract, and seemingly reluctant to extend his deal, they may rather sell now when they can still receive decent money, than in January when they would receive a much smaller fee, or next summer, when they'd get nothing.