In an interview with a French newspaper, Diarra admitted that he is disappointed with his role at Upton Park and keen to seal a move away during the January transfer window.
Despite conceding that he understands Diarra's viewpoint, Allardyce has insisted that he will only look to sell the defender if the two have a discussion.
"He is obviously clear, without telling me, that he is not happy with the situation, which is understandable," Alladyce said. "You get this all the time as a manager when you bring a player of his experience and calibre over from France.
"It is a fact of life, whereas I look at the situation and play what I consider the best team and because of Alou's long-standing injury he has found it hard to adjust to what is needed in the Premier League. If he is unhappy, he just has to tell me what he wants to do and we'll see how we go from there."
The 31-year-old joined the Hammers in the summer from Marseille.