London: Manchester United manager Sir Alex Ferguson has called on football chiefs to take a hardline stance against any new incidents of racism in the sport.

In an interview with CNN, Ferguson said he was at a loss to explain the re-emergence of the problem in English football following Luis Suarez's eight-match ban for racially abusing United defender Patrice Evra.

"I don't understand at all where it's coming from," Ferguson told CNN.

"This is a moment where we have to take stock and we should do something about it if it's surfacing again, and be really hard and firm on any form or shape of racism.

"There have been a couple of examples recently which is not good. In 2012, you can't believe it. It was obvious maybe 20 years ago and the improvements have been for everyone to see.

"I have had some fantastic black players, absolutely magnificent black players, and with every one of them I have enjoyed my working relationship with them."

Ferguson's comments come as Liverpool striker Suarez prepares to face United on Saturday for the first time since the two club's acrimonious meeting at Anfield in October.