Hereford's official website http://www.herefordunited.co.uk say "The game has been moved to Sunday 27th January. No kick off time has yet been agreed."
Cardiff Chairman Peter Ridsdale is still hopeful of a Saturday match.
"We hope the game is a week on Saturday as scheduled, but Hereford are staging the tie, so it's up to the police."
He added: "I don't see why the match would be that high security because our supporters have been magnificent recently and certainly at Chasetown is was a carnival atmosphere."