The Ivory Coast international moved to France last summer having spent six years in the Premier League with Chelsea, where he made over two-hundred and fifty appearances, during which he scored sixty goals.
Last season, the 27 year old scored fourteen goals in twenty-eight Ligue 1 appearances, though the Mastiffs fell just short of European qualification.
Sam Allardyce is keen to further his attacking options ahead of the new season, and has already smashed the club’s transfer window to bring in Andy Carroll from Liverpool.
The England international is almost certain to lead the line for the Hammers for the forthcoming season, something which could scupper the deal with Kalou believed to favour a central position.
Carroll was the club’s top scoring striker last season with seven league goals, while fellow forwards Ricardo Vaz Te and Modibo Maiga contributed three and two goals respectively.