N'dong has been put up for sale by Sunderland this month, as they feel they could raise some money by selling the midfielder.
And West Ham are believed to be interested in the Senegalese international.
N'dong is one of Sunderland’s few saleable assets, and Chris Coleman could look to cash in to raise funds for his own planned additions.
Whether West Ham would be willing to pay Sunderland’s asking price for N'dong remains to be seen.
Sunderland are looking for around £8 million for the midfielder, who has been rotated in and out of their side this season.
David Sullivan has promised that West Ham are looking to invest today, but their progress in the transfer market has been slow so far this month.
The Hammers have brought in just one new player, with Joao Mario arriving on loan from Inter Milan.