The 32-year old midfielder asked to be loaned to French club Rennes after a dismal beginning to life at Upton Park which yielded him just three Premier League appearances in the opening half of the season.
But he is now back from Rennes and looking to become a regular in Sam Allardyce's Hammers side.
"I want to fight this season with West Ham," Diarra told the club's official website. "I'll give 100 per cent in training and I'll wait for my chance.
"I want to give my best for West Ham and we'll see. I'm ready to play in the Premier League now.
"Pre-season has gone well. We work hard every day, and we've only lost one game so it has been a good start for us."
He added: "There are three weeks left to get ready for the Premier League and I want to fight this season with West Ham."