Rostov's initial offer, believed to be in the region of R5 million, was turned down and Neeskens has cautioned that Rostov must put in a "better offer" this week or the player is staying put.
"I told them (FC Rostov) I want to know what's going on this week and if not the deal is off," he says.
The Dutchman insists Xulu is a quality young defender and the price must therefore reflect his talent.
"If you look at the quality of this boy (Xulu) then I don't think they (FC Rostov) put in the right price. If that club wants him badly and they believe in his qualities, they should come with a better offer. It is not that we are not cooperating and I spoke twice with him (Xulu), so we are cooperating. If the deal doesn't go through, then he is committed to us," he says.
Neeskens also leapt to the defence of Sundowns, who have been accused of blocking their players from leaving to further their careers abroad by turning down offers.
"I have always said that if a player has the opportunity, and it doesn't matter who it is, then we should let him go but there is a price to pay. So when a club comes and say ‘we are willing to pay this amount' and Sundowns think the player is worth more, then I can understand that because when Sundowns knock on the doors of clubs to get a player the price goes up," Neeskens claims.
"We gave him the opportunity to go on trial, but if they want to buy a good player they must be prepared to pay. He can go if they come with a better offer," Neeskens concludes.