The News of the World report that top-level talks have already taken place between the two clubs who are on course to meet in a two-legged tie at Elland Road and The New Den.
It is believed they agreed not to allow visiting fans at the matches. With a Wembley appearance and possible promotion to the Championship at stake, police fear violence between football's most notorious hooligan fans.
An even bigger concern is the security nightmare it would cause if the clubs clashed in the final at Wembley on May 24.