Western Sydney Wanderers have delivered a final warning to a "rogue element" of their A-League active support group the Red and Black Bloc — misbehave again and we will shut you down.

In a harshly worded letter to members on Wednesday, Wanderers chief executive John Tsatsimas detailed the zero-tolerance policy.

The policy was justified by the high number of "illegal and highly dangerous" incidents that have already occurred in the club's short history, including the ignition of flares and the banner depicting Sydney FC coach Graham Arnold engaged in a sex act during February's Sydney derby.

Tsatsimas lamented that the incidents had "cost the club immeasurably" not just financially, but also sullied their image as an inclusive organisation.

Three days before the Wanderers put themselves on the global stage in Saturday's friendly with Arsenal at Sydney's Olympic stadium, Tsatsimas issued an ultimatum to a minority of fans.

"Notice is hereby given that should any of these incidents happen this season, including use of flares or other incendiary devices, violence, pitch invasion, discriminatory behaviour or acts that constitute a failure to live up to the terms of admission into the venue, then the club reserves the right to close down the active support area for an indefinite period as outlined by the club," the letter read.

Tsatsimas said all non-offending members would be redeployed to other available seating.

The Wanderers have only just escaped a suspended points penalty that hung over their heads all of last season after lighting of flares by fans.

AAP