The well-connected Turin daily, La Stampa reports Vidal has given the green light to a five-year contract worth £182,000-a-week at Old Trafford.
Italian champions Juventus are now demanding a final decision from Vidal on whether he plans to leave.
United will have to smash their transfer record to get the Chile midfielder.
Juventus want the Red Devils to stump up £47m for his services.
For the big stories and the banter follow us on Twitter: @tribalfootball