Bernard Mendy is set to snub a move to Sunderland in favor of Marseille, but the defender's current club Le Havre insist any interested side will have to match the offer made by the Black Cats.
Le Havre president Jean-Pierre Louvel has accepted a bid from Sunderland for Mendy, and is now waiting to see if Marseille will be willing to make the same kind of offer for the teenager.
"We have an agreement with Sunderland, but not with Marseille," Louvel told L'Equipe. "There are no offers at the moment. Nothing has materialised.
"Marseille's offer should not be lower than that of Sunderland's.
"Everything will depend on Marseille's proposal. I have nothing against OM and I have a very good relationship with (president) Vincent Labrune.
"About the price, I have a confidentiality agreement with the English club, so I cannot tell you anything. But what is certain is that Marseille's offer should not be below that of Sunderland."
Reports in France suggest Mendy has already been to Marseille's preseason training camp where he underwent a medical; however Louvel is not too concerned by those developments.
"It does not shock me that he goes to visit Marseille," he added. "That sounds very normal for him to make his choice.
"But he knows that, to seal a deal with a club, you have to have the green light from Le Havre. And I repeat that we do not negotiate below what Sunderland have offered."
Meanwhile, Jozy Altidore is on the verge of completing his move to Sunderland, with the American international set for a medical on Monday.
Altidore revealed he had agreed a move to Sunderland on Friday, before quickly taking the report from his official website.
However, with Sunderland having agreed a fee with AZ Alkmaar and Altidore believed to have given his nod on personal terms, it only seems like a matter of time before the 23-year-old is officially unveiled as a Sunderland player.
