Manchester United boss Sir Alex Ferguson says he can't stop Rio Ferdinand tweeting.

He admits he can't understand Twitter.

But Ferguson told the Daily Mail: "I don't understand it and I don't know why they do it. I can't understand why people can bother themselves with it, to be honest. As long as they don't talk about the team, and he's well aware of that, then it's OK. I don't think we can stop him."