For decades it has been a source of bitter rivalry among Iran’s vast army of football fanatics. Now the Persepolis v Esteghlal Tehran derby, often a scene of crowd violence and angry on-pitch confrontations, is to be transformed into a tool of football diplomacy thanks to plans to stage the match on US soil. Iran’s two biggest clubs are understood to be planning simultaneous American tours culminating in a fixture between them. The plan was disclosed by the Persepolis manager, Abbas Ansarifard, who said his club had sought permission from the Iranian foreign ministry.