The Mirror says Benitez is set for a transfer breakthrough by landing defender Lejeune.
United will pay £10m up front for the Eibar stopper who can also play defensive midfield.
The former Manchester City contracted player, 26, would be Benitez' first big buy of the summer and he is also searching for a new keeper.
Former City keeper Willy Caballero is an option with Mats Selz heading to Anderlecht.
Newcastle also hope to land Chelsea England U21 star Tammy Abraham on loan.