MLS has sent a letter to half of the league's fan clubs, ordering them to clean things up in the crowd.

Real Salt Lake were one of the clubs targeted by the league for consistent chanting using obscene language and MLS officials want is stopped.

RSL fans have been using the 'You suck a***' chant towards opposition goalkeepers for years but it came to a head during a World Cup qualifier at Sandy's Rio Tinto Stadium in June and supporters of the club have now been warned.

"The response from the world via Twitter, Facebook, international media… was, 'Really Utah, that's what ya got? That's how you're going to represent yourself?'" Trey Fitzgerald, Communications Director for Real Salt Lake, told Fox13.

"After games you hear from people who've had a bad experience and they threaten to not purchase future tickets or to change their plans when they were going to become a season ticket holder."

RSL officials say they are planning to negate the language from the fans for fear that the league may take further action.

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