Niang currently plays for French side Strasbourg and has also attracted interest from Tottenham, Everton and Marseille.
The powerful strikers agent told skysports.com; “There has been a lot of interest in Mamadou and to be fair West Ham are very interested in him.
“We have held very positive discussions with West Ham and we are still trying to iron out a few issues and find out which is the best option for Mamadou.
“Marseille are also interested in Mamadou and I think it is a battle between West Ham and them for Mamadou.”