Forest want the centre-back as part of Steve Cooper’s plans to strengthen the squad ahead of their first season back in the Premier League in 23 years.
Niakhate is a big target for the club and Nottingham Forest are pushing to land the defender in the ongoing transfer window.
But negotiations with Mainz are turning out to be a major problem for Nottingham Forest and their opening offer was rejected out of hand.
The German club felt that the bid from the newly promoted Premier League club was derisory in nature, according to Sky Deutschland.
Nottingham Forest have reached a verbal agreement with the player, who wants to play in the Premier League next season.
But Mainz are now threatening to call off the negotiations with Nottingham Forest after rejecting the first offer.
The club hierarchy do not want to continue the talks with Nottingham Forest despite the club pushing to get their hands on Niakhate.
The Frenchman is keen on a move to the City Ground but for the moment the negotiations between the two clubs have become complicated.
