Arsenal manager Arsene Wenger reportedly tried to sign the former Chelsea striker during the January transfer window, but his failed attempt sparked reports of interest from rivals Liverpool and Tottenham.
However, Bundesliga side Borussia Monchengladbach who are now said to be leading the race to sign the 29-year-old.
Kalou, who scored 16 goals for Lille last term, joined the Ligue 1 side in 2012 following his spell at Stamford Bridge and now admits his future is yet to be decided.
“My departure from Lille? It is 50-50,” Kalou told L’Equipe. “The German league is good for forwards.”
Lille are reluctant to lose the services of Kalou as they bid to reach the group stages of the UEFA Champions League.
Their qualification campaign continues on Tuesday as they look to overturn a one-goal deficit in Porto after losing 1-0 to the Portuguese side at Stade Pierre-Mauroy last week.