The Brazilian full-back emerged as a top target for the Blues over the summer, although the deadline passed with no deal done.
A new contract in Turin was then mooted for the 26-year-old defender, but that has not happened either and the exit door remains open.
United have now joined the scramble for his signature, as Jose Mourinho seeks to bolster his ranks in a problematic area of the field, and Juventus claim they will not block any want-away stars from leaving.
Club director Giuseppe Marotta told Rai Sport when quizzed on Alex Sandro’s future: “The policy of Juventus is that if a player asks us to leave, we will not hold him back.
“On Alex Sandro, we know of the interest from big clubs, but at the moment we have not engaged in any negotiations.”
While departures could be sanctioned in January on the playing side, Juve believe stability will be secured in the dugout.
Head coach Massimiliano Allegri is into his fourth season at the helm and Marotta believes the former AC Milan will stick around for some time yet.
He added on a manager who has delivered three successive Serie A titles: “He still has a two-year contract, but he will stay with us for a long time.”
Along with helping Juve to cement domestic dominance, Allegri has also won the Coppa Italia on three occasions.He has, however, been unable to land the Champions League crown, with the Bianconeri having suffered two final defeats during his tenure.
“Last year we missed the icing on the cake, this year we will try again, the Champions is always our first goal,” said Marotta, with Juve bracing themselves for a last-16 encounter with Tottenham in this season’s competition.