Sevilla, where he impressed on loan last season, have since gone on to sign Marcos Acuna from Sporting.
That appeared to put Man United in the clear for 23-year-old Reguilon, but Spurs have made a big play for him.
According to Ornstein, a deal for Reguilon is not done yet, but is ‘highly possible’ after progressive talks took place.
United have held talks with Madrid for Reguilon, but have been unable to reach an agreement.
Spanish reports have suggested that Madrid’s demand for a buy-back clause has been a sticking point for United.