The 31-year-old, who has slipped down the rankings since moving to Upton Park last summer, has claimed that he is not part of manager Sam Allardyce's future plans.
"I want to leave," Diarra told L'Equipe. "I've tried to stay positive right up to now. I want a real challenge, and I won't get it at West Ham.
"With the current coach in charge, it's impossible. No-one's told me directly, but I'm not stupid. I'm not part of his plans. I have to leave. Some clubs have already contacted West Ham. I'm not afraid to change countries. It'll still be better than here."
Diarra has made just five appearances for the Hammers since moving to the Premier League from Marseille.