Diarra missed training on Friday and Saturday after complaining of stomach pains while scaling a glacier with his team-mates at France's pre-World Cup training base in the French Alps here on Thursday.
"Following the intestinal problem he contracted on the glacier at Tignes, medical examinations discovered an unforeseeable illness that necessitates rest for an indeterminate period," read a statement on the French Football Federation (FFF) website. "As a result, Lassana Diarra is out of the 2010 World Cup in South Africa. For the moment, the staff have not called up another player."
France coach Raymond Domenech took a 24-man provisional squad to Tignes but does not have to submit his final 23-man squad to FIFA until 1 June. Les Bleus begin their World Cup campaign against Group A rivals Uruguay in Cape Town on 11 June.
Diarra joined Real Madrid from Portsmouth in January 2009, having previously played for Chelsea and Arsenal. With Lyon's Jeremy Toulalan he forms Domenech's first-choice defensive midfield partnership and he played in 10 of France's 12 matches in their 2010 World Cup qualification campaign. Arsenal's Abou Diaby played in his position in France's training session on Saturday afternoon.