The Tannadice team are believed to value the Turk – a scorer of 16 goals last season – well in excess of that figure.
Ciftci signed for United in 2013 from Dutch side NAC Breda and has netted 33 times during his two campaigns in Scotland as he has made a notable impact.
The 23-year-old has courted controversy too, however, and was charged by the SFA in May for allegedly biting Dundee player Jim McAlister during a match.
He will find out what punishment if any he will receive next month, with United remaining ‘fully supportive’ of the player since the incident.
Ciftci was also red carded against Inverness in October 2013 after he was accused of grabbing a linesman by the throat.
That charge was later ruled to be unproven and his dismissal was reduced to a yellow card, although he was given a two-game ban for excessive misconduct with one suspended.
Although Ciftci has gained a reputation for petulance, he has also attracted interest from elsewhere and Celtic are keen to make him their third recruit from United in 2015.
Middlesbrough are another team Sky sources understand are interested, while a number of clubs from the UK and abroad have contacted Tannadice about his availability.
Celtic signed United pair Stuart Armstrong and Gary Mackay-Steven in January for a combined fee of around £2m.
Ciftci initially signed a two-year deal on Tayside but extended his contract and has one year of his current agreement remaining.
He rejected a second extension in early June, saying then he wished to move on once his terms expired.
Ciftci told the official Dundee United website on June 9: “I have decided after three years at Dundee United I will be looking for a new challenge.
“I’m satisfied with my development so far and therefore I must thank the coaching staff who played a big part in that.
“I would also like to thank the fans and the club, who have always been behind me.”